ASP.Net String Assignment Failure

I'm having an odd problem with an ASP.Net page.I'm getting an object not set error message when assigning a string literal to a variable. [code] And here is the code that the error is pointing to. The last line in this fragment is the line 10 the error is complaining about [code] It seems it fails on accessing any reference type, even if it is declared locally in the load function. I originally found the problem when Request. IsSecureConnection was nulling out on me. I eventually discovered I could replace it with the above code and fail in the same way. The problem does not always happen. It seems to be triggered by publishing an update from Visual Studio, or when I head home for the day and the server sits idle all night. One or two app pool recycles seems to clear it up, and the page functions correctly. I've been doing desktop development for a few years, but I'm fairly new to web development.So maybe this is something obvious I've got configured wrong. I'm currently using .Net 4 on IIS 6. That code is in a foreach over an IEnumerable(of XElement). The stack trace still points to the string assignment, but all other stack traces are spot on, so I don't think it's a bad pdb.Also, when the error occurred this time, no amount of recycling the app pool or stopping and starting it would fix the error. I finally got it working again by switching the application to a different app pool.