What do you mean? Are you trying to view your entire contact list, including offline contacts? Or are you trying to set the window to-fit your contacts list? Maybe a little bit more info and I could help you out , by the way, which version of Trillian are you running? I'm running the Astra version.
Trillian used to constantly give me problems... and honestly. I've faced issues kind of like this, and then eventually my accounts just stopped connecting.
Best advice I can give is make the switch to Pidgin. I used Trillian for YEARS but after having too many issues... I made the switch and am probably not ever going to go back.