A Javascript error i can not fix

Had it all working and then had a memory crash dump and since then i get
A Javascript error occured in the main process pop up
tried removing install and re installing and get the same pop up during install
i have search both your support site and google and not found solution
one chap said he fixed by deleting the local app data
what and where is the local app data
surely this is renoved with uninstall any way ?

running on windows 7