Hi Tim,
Things I would do to troubleshot this:
check that the hosted environment is ASP.NET 3.5 SP1
check the mojoportal log for clues under Administration Menu > System Log. Note that the newest errors are at the bottom and there will be plenty of errors in the log after an initial install, so it may be best to clear the log, then visit a few pages then check the log again.
I would look at the data in the mp_Pages table and look for problems, like blank url field or name field or anything that doesn't seem right.
Are you working with source code or a release package of mojoPortal?
Did you deploy your own build to the host or one of my pre-compiled release packages?
Hope it helps,
Joe