This connetion problem has been around for a long time. I'm running an iMac 500 with 192 Meg of Ram and have had these connection problems with versions 1.6 b and d. Intial connection would be made but the longer i'm on line the less host i have before eventually i just can't connect anynore without a certain ammount of fiddiling with the connecions tab.
I hoped this problem would be fixed with 1.7 but it looks like i'm still stuck with Aimster!