problem opening avast

I recently installed avast antivirus, however upon trying to open it i get this error message "the application has failed to start because its side-by-side configuration is incorrect. please see the application event log or use the command-line sxstrace.exe tool for more detail."

when i went to the event logs it said this

"Activation context generation failed for "C:\Program Files\Alwil Software\Avast5\AvastUI.exe". Dependent Assembly Microsoft.VC90.MFC,processorArchitecture="x86",publicKeyToken="1fc8b3b9a1e18e3b",type="win32",version="9.0.21022.8" could not be found. Please use sxstrace.exe for detailed diagnosis."

when i tried to use sxstrace it would just open quickly and close, i'm not quite sure how thats supposed to be used, with this info can anyone help me?