I was having a similar problem with IDEFix about the same time this morning - how strange.
I discovered that when it was trying to mount CD0: it was crashing - I moved CD0 from devs and tried to mount manually and it would crash again. I got around it by removing IDEFix and using a different filesystem and CD0 entry.
I use classicWB and I think something in IDEfix doesn't like one of the patches - If I boot up in on of the modes which doesn't activate all the patches as it boots, IDEfix works.
