Normally when you get a js error like this it is normally due to one of two things, either the cache file is bad or the configuration folder is bad. Here are instructions for trying both of these things. It sounds like you already did the cache file correctly but I will include those instructions just in case.
Here is a link to the steps to take to rename the configuration folder and undo any corruption that may be present there.
Please give these a try and let us know if the problem persists so we can look into this further with you.