indexing madness

hi all,

i've got an external USB drive connected and spotlight has been sitting for weeks or months 'estimating index time'. also i cannot remove the disk from the desktop - always get the message that it's busy even if it isn't (at least i'm not doing anything with it). it will only unmount when i shut down/restart.

i've read in the forums about trashing the index file from the command line or by removing indexing by adding it to the exception list. i tried the latter and the mac responded with the following error:

Privacy list error
The item coulnd't be added or removed because of an unknown error.

what's up with that? other than the weird indexing, the disk behaves normally. it's a 1Tb drive, about 2/3 full.

diskutility doesn't report anything wrong with the drive ('appears to be ok'). this is on a quadcore mac pro with 10.5.8. i have no other system to test it on.

any ideas?

thanks,
stefan