Hi Jason,
Please add the following auto-updated parameters to your LoadTesting project item and play back your test:
Name: __VIEWSTATE
Regular Expression: \sname\s*?\=\s*?"__VIEWSTATE"[^^]*?\svalue\s*?\=\s*?"(.*?)"[^^]*?>
Replacing Mask: $1
Name: __EVENTVALIDATION
Regular Expression: \sname\s*?\=\s*?"__EVENTVALIDATION"[^^]*?\svalue\s*?\=\s*?"(.*?)"[^^]*?>
Replacing Mask: $1
Name: d
Regular Expression: \ssrc\s*?\=\s*?"/WebResource\.axd\?d\=(.*?)&
Replacing Mask: $1
Name: t
Regular Expression: \ssrc\s*?\=\s*?"/WebResource\.axd\?d\=.*?&t\=(.*?)"
Replacing Mask: $1
Name: d
Regular Expression: \ssrc\s*?\=\s*?"/ScriptResource\.axd\?d\=(.*?)&
Replacing Mask: $1
Name: t
Regular Expression: \ssrc\s*?\=\s*?"/ScriptResource\.axd\?d\=.*?&t\=(.*?)"
Replacing Mask: $1
If the problem persists, please zip your entire project suite folder along with the log of the failed test execution and send me the archive. Make sure that messages in your log correspond to the latest version of your tests.