Membership.ValidateUser always returns false after upgrade to VS 2010 / .NET 4.0

Not sure whether this pertains to VS 2010 or to the upgraded framework, but… we are using the Oracle membership provider to authenticate users. Prior to the upgrade everything worked fine, but now Membership.ValidateUser(user, password) returns false despite valid credentials. There is no exception thrown, so it’s hard to determine what the problem might be. The website administration tool in VS 2010 is still able to manage users and roles (more or less), so I have no reason to question connectivity. What might the problem be?

Is it OK to use static variables to cache information in ASP.net?

At the moment I am working on a project admin application in C# 3.5 on ASP.net. In order to reduce hits to the database, I’m caching a lot of information using static variables. For example, a list of users is kept in memory in a static class. The class reads in all the information from the database on startup, and will update the database whenever changes are made, but it never needs to read from the datebase.