QuickLook stopped working What might cause quicklook to 'freeze', as it were.

quicklook has gone south to some degree, some files are QL-able, other not, 
and we're speaking of the apple plug-in type (pdfs, txt, jpg, etc.)

Even whilst running the Topher 'fix', terminal hangs 
after either the qlmanage -r or qlmanage -r cache.

Cheers, and thanks in advance for any light 
your available time might hereby shed. :)

Running OSX, ver 10.6.6 on an iMac
It is possible that some QL plugins are broken, you should check 

~/Library/QuickLook/
/Library/QuickLook/
/System/Library/QuickLook/


for new QL plugins (check the date of the files). Maybe a program installed a new (broken) plugin? But some QL plugins are not inside the Library/QuickLook/ folders you can use

qlmanage -m


to list all QL plugins, with

qlmanage -m | grep -v com.apple


you see only plugins which are not from Apple.