When exporting to media, sequences in Premiere Pro CS6 sometime just stop rendering to media (with no error warning)...until I restart the program. Other times the same sequence will report an "error" for "unknown" causes. This generally happens on a 2 pass variable export rendering to H.264.... but almost never on a CBR renderings. It is almost always solved with restarting Premiere.
I'm not sure if this is related, but I just built a new system with a terabyte solid state drive and reinstalled CS6 when it seems that these errors began. The preview renderings are being saved to a partition on this drive, but the export renderings go to a different normal spinning Sata drive.
Others have reported the same thing, and I saw it happen once but can't tell what combination of factors is causing the encoder library to fault. Queuing the sequence into AME doesn't seem to help, nor does rendering with previews.
The 'workaround' is to export from Premiere in another, high-quality format (e.g. Cineform AVI) then use Media Encoder to convert to H.264. I can't make it crash in standalone mode, even with VBR2.