I cannot find any reason for this. Our software does not pass your credentials to any server other than Betfair's. I would first check if your proxy settings have changed. Betting Assistant will automatically use the same proxy settings as Internet Explorer.
Here are instructions for checking the proxy settings.
http://windows.microsoft.com/en-gb/wind ... =windows-7
If it's configured to use a proxy then disable this and try it again. If you are not using a proxy then you will need to refer this to Betfair. I recommend contacting the API team at
bdp@betfair.com as customer services may try to refer you straight back to us.