Javascript error

I have uninstalled en reinstalled all CSS Design suite extensions: directly after activation of Theme-it same Javascript error message
At that time there was no WinFileCache.dat file
I have tried theme-it with new CS5 layout files: sometimes theme-it starts without a problem, sometimes it starts with the javascript error
I have tried it with html files and dwt files: sometimes theme it works sometimes javascript error.
I have tried theme-it after creating a CSS Sculptor page and it worked without a problem. After that the WinFileCache.dat file was back again. When I launched Dreamweaver and saved a new html file (based on a CS5 layout) I again got the javascript error.
My impression is that theme it works with pages created with CSS Sculptor (allthough I am not 100% certain that it always works in that particular situation), but that theme it is unstable with pages created bases on CS5 layout.

The solution provided in Common Installation Issues (deleting the cache file) is not a satisfactory solution: it would require deleting the cache file everytime and even then I have noticed that in the absence of the cache file the javascript problem can still pop up. So I would really like to hear about a structural solution.