Welcome to Infragistics forums and thank you for the detailed post. I wish all question are detailed like this one J
The reason for the issue you are experiencing after installing TestAdvantage is due to the version compatibility. The version of TestAdvantage proxies has to match the version of NetAdvantage controls in order to work fine. So for example the TestAdvantage version you downloaded from our website is 2008 Vol 3 which means it works only with NetAdvantage 2008 Vol3 and my guess is that your application is built with a different version of NetAdvantage. Can you check with your developer what version of NetAdvantage he/she is using so I can send you the link to the right installer. Once you get the correct version installer you just have to uninstall the current version you have right now (2008 Vol 3) and install the new one.