Can't save illustrator docs anymore!!

I know a lot of you guys use Adobe's Illustrator out there and I've got a real conflict going on so I hope someone can help.

I have 2 Macs running CS. The laptop has suddenly developed this problem. I can create a new document or load an existing doc, work on it etc, but if I add any amount of text and attempt to save it I get firstly : 'an unknown error has occured', once I click 'OK' then I get 'Can't save preview, but all other information was saved. The file couldn't be found ID= -43'. Needless to say nothing gets saved.

I had noticed something odd though. In the character palatte, while I could choose a font from the drop down menu, no chosen font name showed up in the box - that was the first indication that something was wrong. I've run fontdoctor on the fonts with no issues being reported. I've tried trashing the prefs, caches, repairing permissions, reinstalling - nothing helps. I've ruled out user issues by launching a second user and trying it in there - same problem. I really need to use illustrator on the laptop. Any help would be really appreciated.