It seems a few people have experienced problems with these SIMMs dying after some time when runnign at 60MHz on BlizzardPPC cards. The 240MHz version uses a 60MHz FSB (the 50MHz is the 680x0).
It's strange because a lot of these large capacity SIMMs were designed at a time when 60/66/75 MHz FSB speeds were quite common for PCs that used them :-?