We noticed people talking about this yesterday, and I'm going to be looking into this today; however, it is quite difficult, as people keep conflating issues related to WinterBoard itself, issues related to WinterBoard that are unleashe by the new builds of Substate that have the 6.x-compatible MSFindSymbol implementation, and conflicts between WinterBoard and other extensions.
Like, what I really need to know from people is 1) does this happen with no themes installed, 2) does this happen with only WinterBoard and no other extensions (and thn, which other extensions cause it), 3) does this happen with Substrate 0.9.3999.6 (downgrading from 0.9.400x), 4) does this somehow get fixed by some earlier version of Substrate.
As it stands, from what little I've heard, it is simply "a recent update of something (users always say "WinterBoard", but that doesn't really make much sense, honestly, from the code that was changed: they must mean the corelease of Substrate... WinterBoard barely even needed to be updated) causes this issue, but only "if you have other extensions installed" and (maybe?) it happens without any themes.
On my end, we reproduced what looks like one of the logged error messages that may be causing the killing (something about running ou of vnodes) last night, and can spend some time whittling it down, but there is no guarantee that our lab conditions are really reproducing the problem.
As this supposedly is "recent" (as opposed to "6.1+WinterBoard") this is probably fixable without that much pain: the problem is just going to be figuring out where the issue is (and again: even if WinterBoard correlates with the failure, the actual problem could be in Substrate or in a third-party extension).