Some time ago we found this problem when you do not have Project license key and you try to access the Electronic Time Card in Enterprise Portal. While  you click on the drop down of ''Category'' field to select values it throws an error

Not enough rights
Problem can be fixed in very wasy way: do not show field category to end user: Go to AOT \ Web \ Web files \ Web controls \ JmgEPJobRegistration and double click on it the edit window will apeare Look for line:
<dynamics:AxBoundField DataField="ProjCategory" DataSet="JmgEPJobRegistration" DataSetView="JmgTimecardTrans" SortExpression="ProjCategory" AutoPostBack="true"/>
and replace it with
<!--<dynamics:AxBoundField DataField="ProjCategory" DataSet="JmgEPJobRegistration" DataSetView="JmgTimecardTrans" SortExpression="ProjCategory" AutoPostBack="true"/> -->

To apply changes you need to run AxUpdatePortal: http://msdn.microsoft.com/en-us/library/dd261467.aspx