rubygem problems (maybe just on MacOS 10.4)

[Vassilis Rizopoulos]

It looks like there is a problem (I don't know if it is Mac specific -
although I do not think so) with gem and proxies:

meisterbrau:~ riva$ gem update --http-proxy http://my.proxy.com:8080
ERROR: While executing gem ... (NoMethodError)
undefined method `[]=' for #<Gem::ConfigFile:0x1087518>

I have a Macports installation

meisterbrau:~ riva$ ruby -v
ruby 1.8.5 (2006-12-25 patchlevel 12) [i686-darwin8.8.2]
meisterbrau:~ riva$ gem -v
0.9.1

Any ideas?
Cheers,
V.-