What version of Orchard are you using (official 0.8 release or recent dev branch)?
This error usually happens when one of the modules (or themes) can not be loaded or compiled by Orchard. We made changes recently in the dev branch to give a more precise error message.
In the meantime, you can try a couple of things:
1. Delete all the ".csproj" files under "~/Modules" and "~/Themes". These files are only needed if you want to be able to change .cs source files on your deployed server. Restart Orchard and see if that solves the problem.
2. Edit the "~/Config/Diagnostic.Config" file and change the "initializeData="c:\logs\orchard-debug.txt"" attribute to point to a directory writable by your asp.net server on your deployed machine, then change
"<source name="Default" switchValue="Error">" to "<source name="Default" switchValue="Warning">". Finally, change " <trace autoflush="false"/>"
to " <trace autoflush="true"/>". Restart Orchard, and take a look at the log file for exception messages. They should help you diagnose the problem. Note you should revert the config file to its original value once you
are done, as leaving these values are some performance impact.