My A1200 has had this really annoying and persisting problem ever since i changed hard drives.
Sometimes hard drive access will just freeze.
Some typical situations where is sometimes (10-20% of time) happens:
Loading workbench @ loading MagicMenu
Loading a any apps, be it Whdload games or anything else
Transferring files
The hard drive is a 20GB Toshiba 2.5" laptop drive. It is formatted using SFS and has 3 partitions all of them less then 1.5GB in size.
I did all the correct settings for SFS in HDtoolbox including setting the buffers to 100 etc.. etc.. and i always pressed ENTER after entering the values and everything saved as its supposed to have.
The hard drive is connected to the A1200's internal IDE port. There is also an IDE CDROM drive attached to the same cable. I have IDEfix installed.
I also checked that everything was plugged in properly.