here's what i can tell you, and i need to repeat, i am not a fan of official agnitum support team, and im not a salesman for outpost
1) i've been using outpost for several years now, and it has been rock solid stable for me. ie it never crashes, never bluescreens.
now obviously you've got an issue, and you're not the only one given the forum, but it does mean that in general its not a buggy app, and given the volume of traffic on the forum it shouldnt be surprising to find some others with bluescreens.
2) outpost is actively developed, and win xp sp2 is a big user base, so i would be quite sure they care about making it stable on this platform.
i can only suggest to keep looking to try to figure out what is making it freak out - clearly its a problem not with you but with the app, but maybe you can try to figure out what is triggering it.. some other app may be trying to make a specific connection, or something like that.. actually there was a known bluescreen issue that a friend figured out a cause for.. it had to do with a certain cygwin-compiled app trying to establish a connection.. see if you can figure out what is causing the bluescreen... try disabling all plugins.