I installed thinkorswim ("ToS") to Ubuntu 10.04LTS on a 64-bit AMD setup in January and used it without issues through August 3. The system was continually kept updated all that time.
In mid-August I attempted to install ToS on a different 64-bit AMD computer under a fresh 12.04 install (with updates). Although ToS installed and ran, it crashed the system. The only way to recover is to remove the battery. Installing Sun Java 6u35 solved the problem (see post "Thinkorswim crashes 12.04"). ToS will now install and run, but the kill button causes the ToS icon to disappear and the only way (that I know of) to restart ToS is to reinstall (run the ToS installer script). Minimizing also causes problems. The 12.04 update of October 10 has only made the problem worse (kill/minimize/maximize buttons disappear, buttons respond only after very long delay).
Also, ToS will no longer install to a fresh 10.04LTS install. (first observed in mid- to late September on a third 64-bit AMD setup). The script runs, but the Java installer fails, emitting a message saying that it cannot connect to an X server. Attempt to install to openSuSE 12.2 fails also. Installing Sun Java 6 makes no difference.