I've been trying to use the Excel Connector for the last two weeks to manage the data in our organisation, but I'm having a problem where I get the following error in Excel which is preventing me from using this tool:

Error Generated by request::An internal server error has occured while processing your request.
Url:https://www.salesforce.com/services/Soap/c/13.0

ExceptionCode : 5103

The first couple of times I tried to use Excel Connector it worked fine. However I then started seeing this error every time I tried to use it - the error appears after I put in my password in Excel Connector and click Login.

We are on Salesforce Professional. I have tried uninstalling and reinstalling the toolkit and connector, but it hasn't made a difference. I'm using Excel 2010 32-bit on Windows 7 64-bit.

I can log in to Salesforce in my browser on the same computer.

I've checked that IE is not in Offline Mode, and verified that Excel can actually connect to the internet (pinged a URL using VBA script).

I've tried disabling my antivirus (MSE) and windows firewall.

I've tried changing the server url as suggested by this thread (had to modify registry keys to do this as that field was not editable in the connector.

None of these resolutions worked.

Has anyone experienced and managed to resolve this, or can anyone suggest any other possible resolutions?