Interesting...
The bug seems to have been triggered by the attempt to render a failed/aborted rigged mesh on an impostor:
Relevant log lines:
Stack trace:
The crash happened while you were caming because it caused a mesh LOD change and the new LOD was obviously one of the failed mesh data downloads...
In fact, every viewer would have crashed at this point, since the affected code is shared by all viewers. It's interesting that you got a 408 error on a mesh download request since it's a very unusual HTTP error code that Lindens obviously didn't think they would encounter (it's not handled by their code). This could be the result of a recent change made to the SL HTTP servers...
I added proper handling of error 408 and will "harden" the LLDrawPoolAvatar code against aborted mesh downloads for next releases.