I'm having the same problem as the OP. CPU meter maxes out with no other programs running and just a few charts open in TWS. RAM gets filled up, too. Started with build 912, continues in 913.
Tried replacing the settings folder (Jts folder), no relief.
Not qualified to say the problem is TWS, rather than the nondedicated 2005 iMac G5 running OS 10.4.11 or the loose nut on the keyboard. But TWS is where the problem is showing up; other programs seem to work ok.