Simultaneous logins using 1 spark client

Hi,

We have 2 servers with different domains and separate users. Each user has spark client installed on thier work stations. As few users have to login into BOTH servers (seaparate login/domain/password), is it possible for them to login into both server simultaneously so that they will be able to IM with other users simultaneoulsy (something like yahoo multi-gold)

Pl advice.

TIA

Prvn