>>> how can I force gem to update the index? Somehow my gem  
>>> installation seems to be a bit confused when running whith super  
>>> user privileges:
>> Looks like most issues disappear if one deletes the file
>>   source_cache
>> located in the directory
>>   gem env gempath
> Thanks, that helped!

Ok, 1 fixed, 1 new:

[mbp:~] th% sudo gem install rmagick
ERROR:  While executing gem ... (OpenURI::HTTPError)
     300 Multiple Choices

What's wrong here?

Timo