Slippy grit?

I was wondering if anyone's been having traction problems on gritted roads. A mate down in the west country tells me there's a bit of local concern following a few spills and near-misses on recently gritted roads. He's raised the issue on the Chippenham Wheelers' forum and it's rung a bell with several people. They're wondering if there's a new kind of grit being used… I'm in Brighton and have only been out once on gritted roads this year so far…didn't notice anything untoward. But I thought I'd mention it, just in case.