Well, if you have two classes within the same application domian with the same namespace it would cause issues.  So yeah, that could be part one.

the second part is, if your just opening the ascx and vb file, intellisense may not pick up the references to other classes, the global, or anything in the bin or app_code folder.  So it's best to open the solution and then you will not get reference errors. 

Given its dynamically compiled on first load you can simply save the file with these errors showing and it wont make a difference.  however, as we can see with the namespacing this could be causing issues.  My recommendation is to take on of Michaels tutorials from www.adefwebserver.com and follow those.  I think he also posted to the fast login which could help.  but i definatly think that by having two classes with the same name within the same application domain would cause some odd exceptions.

HTH,

Chris