Thanks, Nick; I'll check mine tomorrow!
Coincidentally, I was just using mine this afternoon, cutting redi-rod.
I mentioned a while back that I had that exact problem with a 4.5" one from Makita (several years ago). I took it out to the Service Ctr. where I was informed the that it was my fault, I'd obviously been abusing the grinder if it had overheated.
I told them in no uncertain terms that it was their fault for being too ******* cheap to not put in a thermal overload device. They replaced it.
Last turquoise coloured tool I bought.
And that Kiddies is why I buy Bosch.