asp.net Session variables inside of SharePoint

So, here is a problem that I am having with asp.net app inside of SharePoint (as page viewer).

When the Default page is loaded, it works fine. However, when I try to go t开发者_运维问答o next page, i am getting a null reference exception. It looks like my session variables are becoming null on the next page (even though I set them on the previous page). Here are a couple things that I tried to diagnose the problem.

1. I try on the couple other computers; some work fine, some still don’ts.
2. In the property of the page viewer inside of the SharePoint, after I click on the "Test link", it started to work fine until the session expired (on the computer didn’t work initially).

I am not sure if there are settings that I need to check on the browser or the app server. Anyone had similar problem?

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I don't know Sharepoint, but it sounds like either In Proc session state, and the application pool restarts, a webfarm not setup properly, or cookies not being stored correctly. A starter would be to install Fiddler to see which cookies are sent. Then you should install some logging mechanism in your global.asax to know if your application pool restarts. (Might show up in the event viewer as-is, don't remember.)