Apex 4.1 + RESULT_CACHE_MODE (FORCE) = Apex Bug
I just blogged about this bug or the weird thing in my blog:
http://balajichellappa.blogspot.com/2012/05/apex-41-resultcachemode-force-apex-bug.html
In short here is what happening, after upgrading to Apex 4.1 if you set ALTER SYSTEM SET RESULT_CACHE_MODE = 'FORCE' SCOPE = BOTH; then Apex application import will no longer work.
You will see strange values in File Character set drop down.
Just revert back to ALTER SYSTEM SET RESULT_CACHE_MODE = 'MANUAL' SCOPE = BOTH; to make it work again.