Is it a multiple site mojoPortal installation with folder based sites?
If yes, then you might need to add this in user.config:
<add key="UseTransferRequestForUrlReWriting" value="false"/>
If it is just a single site mojoportsal instance and you have installed in a sub folder beneath some other app running in the root folder, and if you are also using https, then you may need to add this to the user.config file:
<add key="IsRunningInRootSite" value="false" />
Hope that helps,