I just had the weirdest problem: I installed two new fans (Zalman ZM-F3's) in my Antec Sonata II case, one as a replacement (at the back) and a new one for additional airflow (at the front). The weird thing about the Sonata is that the 120mm front fan is installed behind the harddrive cage... Like so:
As soon as I installed them, however, my harddrives started messing up big style. My RAID1 array broke (one drive just said it had an error in BIOS) and the other had a corrupt Windows installation (kept hanging on boot).
After many hours with SpinRite and ChkDsk things finally seem to have sorted themselves out (ChkDsk found lots of errors), but during that time I unplugged my new front fan (damn thing wasn't turning anyway)... And it struck me that it might have been to blame?
Thinking about it, we're talking about putting an electromagnet very close to magnetic media... Surely things are better designed than that, right?
(Note: This isn't a picture of my rig, it's just very similar.)