The error you are getting now after going back to UE3 is probably due to a bad cache file or a corrupt configuration folder. Here are the steps that you can take to overcome these issues:
Delete the cache file:
Rename the configuration folder:
You should not have to downgrade back to an earlier version. You say that you updated the UE server behavior on the page and then 'tested the connection and had all kinds of error messages'. Could you elaborate on this further? What were the specific error messages and when did you get them?