done the upgrade from 1.1.2 to1.1.3everything went ok no errors then when reinstalling the 3rd party apps installer crashes so i cleaned up the application folder using shh
removed installerV3.0b10 and put fresh copy it back on using shh
its not crashing anymore but when i try install an app i get
"main script execution failed"

thinking about downgrading back to 1.1.1 it if i cannont find any solutions
any help would be appreicated

You probably need to do the commands listed on the welcome page of Installer.app (chmod/chown etc). I've had to do that again since, too, so I'm not sure what's up. The crashing might be due to low disk space, it was for me - necessitated moving my applications folder to the media partition and symlinking it.