Hi,
Thank you for reporting.
We know of an issue that might be the cause for the problem
http://support.visualwebgui.com/issue/ViewIssue.aspx?id=642
Although I must say that I have some serious doubts that this is the cause, however, this issue will be fixed within version 6.4.
You have been explaining that this issue did not occur in previous versions and this immediately lowers the odds for this issue to be the reason. Furthermore, version 6.3.9 does not contain any new designer/VS integration related issues changes comparing to 6.3.8.
I was thinking that it would be helpful if you provided the following details
* The previous VWG version number you have been working with (before upgrading to 6.3.9).
* The error message you get in VS in this thread.
* I will very much appreciate it if you could re-check this issue with the previous version you have worked with, that of course, if you have a straight forward reproducing path...
Looking forward to any additional info you can provide.
Kind Regards,
Itzik Spitzen