Was at a friends place, he had changed some of his incandescants to CFL's about 6 years back, and a couple of them had failed. Opened the fixture and found that parts of the white plastic internals almost crumbling away when touched, but only where they would have been exposed directly to the light. In another place a red coloured wire crimp (similar to those automotive 3 way crimp blocks) and 2 white cable ties had fallen to bits.
An identical fixture that had been left with the original incandescant was fine.
Im starting to think these CFL's might not be very friendly to non-UV stabilised plastics ?