Can I use Sim-IM to connect my GoogleTalk account?
Yes, you can.
To connect to Google Talk jabber server, use the following settings:
[x] Use SSL
[x] Use plain text login
[x]Manually specify jabber host:
Why ICQ User details do not work properly on systems with utf-8 locale?
Sim-IM detects you language, by the name of you system's encoding. (Strange idea, isn't it?) When you are using utf-8 encoding, language can't be guessed, because utf-8 is for all languages. So you should manually set encoding that should be used for getting ICQ userinfo. This can be done at Setup/User Info/Encoding. (Changing encoding here would effect ICQ). Russian users should choose CP-1251 encoding, German users should choose ISO 8859-15.