I've got a couple questions. The first one is that I can not seem to find the error message related to the error. Can someone tell me when an error occurs in load testing where I can find out specific information about the error?
The second problem (which I may be able to resolve when I know what the error is) is that I recorded a task that would simply log in to the web application, then populate another form and post. When I run this task without modification I get an error right after posting the form. Without knowing what the error is does anyone have any suggestions on what may be causing the error?
An error in load testing usually means that the request being made failed critically to execute. I'm assuming, BTW, that when you say "error" you're seeing the red X in the test log.
Why it failed to execute is up to the application. Sometimes, it's because of a serious error on the application side, sometimes it's because of a server "melt". There are a variety of reasons, most of which you will need to do some investigation in any logs you have available from your actual AUT.
As for the second problem, cookies, sessions, ASP.NET ViewState properties, etc, are all reasons for a failure as you described. You'll need to take a look at the request that received the error (did it happen on the post or on the get?) to determine more closely but I suspect you'll find that something did not match up in the playback causing a critical failure to execute a request.