An (ahem) slightly personal question for the lads!

My sympathies... Had similar problems when I restarted cycling after many years layoff. My solution - a Crane Creek Thudbuster - the short one for city roads. That and a split saddle. Together they make all the difference.
Hope this helps.
Knotty.

If you sit on the "sit bones" - you'll be fine. If you lean forward onto the perineum (the bit behind the scrotum) then you squash the nerves. This is essentially a posture issue/bike fit issue.
Cut-out saddles work by removing the pressure so that your bad posture doesn't cause numbness - but many miles may screw your back.

Spinal flexibility may be a factor in that you can slouch or hunch easier (ie poor posture)whilst keeping your pelvis level.

Sit bone width, as mentioned by many, is the key, as that is the main supporting contact point.

I had similar issues, even with a Selle Italia with a cut-out. However, when I switched to a Selle San Marco Mantra (with giant cut-out), all the problems went away. I now have one on each of my race bike and winter training bike.

I cannot recommend it highly enough (although of course, it may not suit your shape). Flippin' expensive mind you.

Somewhere on the fizik website, there used to be something that explained well why this occurs for some people and not for others. All to do with spine flexibility - if your spine is less flexible, as you reach forward for the handlebars, your pelvis tilts forward instead which presses the soft bits harder into the saddle. People with flexible spines tend to keep their pelvises more upright.

Definately found a cut-out helped; +1 for the toupe and make sure it is level so that your weight is on the ishial tuberosities (sitty bones) and not the perineum. Sore baw-bag either means you need a better pair of shorts or you are using your sack as a cushion - not recommended.

When I returned to cycling in my forties, I found my bum muscles had sagged since I last cycled, and the saddle that had borne me thousands of miles in my teens and twenties now gave me a numb perineum and, cough, beyond. Actually, it's not the numbness that is the problem: it's when the feeling comes back! Now, if you get pins & needles in your hand or somewhere, you are supposed to shake vigorously to restore the circulation. But if it's in your.... well, let's not go there. Suffice it to say that if you're in a public place, all you can do it walk around for a bit with a pained expression on your face, cleats ticking on the tarmac.

So I got a Terry saddle with its cutaway and have never looked back -- but I am no racing cyclist and most racing saddles are too narrow for me at the best of times. You will be in a different riding position on a road bike compared with an MTB, but you might try your MTB saddle as a starting point and look for something with the same width for the sit-bones' position.

Invest in a Brooks saddle. Sorted out my undercarriage issues for good!

Interesting article in the last issue of Cyclist about saddles and there is a school of thought that cutouts actually can make the pressure on your Biffins Bridge even worse by shifting the pressure to either side and stretching it.
Some swear by them though so i reckon its a case of trial and error until you find the right saddle.

Ha, I did the exact same thing as you, Sadly Biggins. Went from an arione to a toupe, via the sit bone measurer.

I had something similar when I first got my bike and was getting numbness from the Fizik Arione which came with it. The first thing I'd do is go into your LBS and have your sit bones measured. You can then check if your saddle is too narrow for your sit bones (the width of the saddle is often marked underneath it). If it is too narrow, your body weight is largely pressing on your perineum, hence the numbness.

As others have said, it could be riding too much or poor bike fit but saddle width is worth checking as it should be free to do this in your LBS.

I found the Fizik Arione painful for longer rides so got measured and then went for a Specialized Toupe Gel saddle (this has a perineal cut-out) and have not had numbness since. I hardly notice I'm on it, which is a good sign so far as I'm concerned.

Agreed re: saddle but you might need to look more widely at your position on the bike and whether your saddle and bars position effectively distributes your weight evenly. Spend a few quid on a bike fit first before adopting a scattergun saddle search. Some people don't get on with the cut-out saddles and prefer the more evenly distributed pressure of something like a Fizik. If you are from an MTB background, there's nothing wrong with using something like a Charge Spoon.

I would also suggest having a week off after your Strava challenges to give your body time to recover and improve. There's another thread here about resting being as important as training:

http://road.cc/content/forum/84941-training-well-vs-mileage-accumulation

Simple choice; new saddle or erectile disfunction! Specialized have put quite a lot or work into this with their Body Geometry range....think there's a Selle Italia "saddle" that is more hole than padding! http://www.selleitalia.com/se_it3/prodotti/road/pagina_max-flite/
Haven't tried it though.

You need to get a saddle that does not do this to you!

Or else.....

http://sportsmedicine.about.com/od/cyclingworkouts/a/BikingImpotence.htm

This site explains it and explains how to avoid it

Take a pin and jab your sack...the feeling WILL soon come back when the blood rushes around.....

WARNING Do not listen to a word I say and trying this may risk your health

May need to fine tune your saddle position and/ or your padded shorts (im presuming you are wearing padded shorts!)
I may be wrong and others may disagree but i would say that perhaps you are riding a teeny bit too much. Its good that you are enthusiastic but it is important to give it a rest now and again and i think that maybe your bollocks are feeling the pressure (literally) of too much too soon.