Looking at the crash dump you sent me, this was caused by an invalid signature in a gamedata file.
There was a long-standing
bug in SM's sigscanner where it would read one byte too many while looking for a signature that didn't exist, in your case this triggered a crash due to exceptionally unlucky circumstances, a new OS security feature, or some 3rd-party (possibly an AV program) security feature.
This is fixed in snapshots later than 1.4.3-hg3494 / 1.5.0-hg3511 and will be included in the next release.
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