After looking at some old posts on this forum I am led to believe this could be caused by one of the following:
- The server you are installing on has .NET 2.0.
- Read/write file permissions are set on the data directory.
- All files from the mojoPortal package were properly uploaded.
It might help to take a look at this post: http://www.mojoportal.com/Forums/Thread.aspx?pageid=5&mid=34&ItemID=3&thread=2186&pagenumber=1.
Hope this helps.