2.0 user control Compilation error

[Guest]

I've just upgraded to using 2.0.
I installed the 2.0 framework and decide to give my previously working 1.1
web app a run.
In odd occasions, I get a compilation error in my page that contains user
controls.
The error is this:
Compiler Error Message: CS0433: The type 'ASP.datetextbox_ascx' exists in
both 'c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET
Files\docconsole\45d0a423\42a4ec7e\App_Web_5ty1a9l4.dll' and
'c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET
Files\docconsole\45d0a423\42a4ec7e\App_Web_datetextbox.ascx.cdcab7d2.rnosksyv.dll'

The page would cease to work forever until I go to that directory and kill
the temp dlls.
Does the user controls in the 2.0 have a new convention of calling/using it?
What's wrong??