This issue is shown when running piglit test suite which will make Xvnc to allocate memory until it dies.
For more information see comment #20 and #22 on bug #1414
We previously ran piglit without problems against ThinLinc 4.1.0, so this seems to be a regression somewhere. Might just be that piglit has new tests though. In any case we should redo the tests against older versions of Thinlinc.
We should also see if we can reproduce this against standard Xorg and see if we can get help from upstream.
If it still turns out to be an issue specific to us then we'll have to rediscuss the priority.
Happens with Xorg as well. Filed a bug upstream:
Should hopefully be gone now that we've upgraded. However bug 3625 is preventing us from running these tests.