OWA http 500-12 application restarting errors

[bazlit]

has anyone got any ideas here, no event viewer errors, just that one in the browser on exchange 5.5 sp4 with these patches installed as well

810579enui386.exe
Exchange5.5-KB818709-v2-x86.enu.exe
Exchange5.5-KB828489-v2-x86.enu.exe
Exchange5.5-KB829418-x86.enu.exe
Exchange5.5-KB829436-x86.enu.exe
Exchange5.5-KB841765-x86.enu.exe
Q283238ENGI386.EXE
Q289258ENGI386.EXE
Q289606ENGI386.EXE
Q301361I386.EXE
Q304062ENGI386.EXE
Q307195ENGI386.EXE
Q312273ENGI386.EXE
Q313576ENGI386.EXE
Q313576ENGI386.EXE
Q326322ENGI386.EXE
Q329415ENGI386.EXE