Issues when upgrading from 3.0 to 3.1 using Application Builder

Hello,

I recently started upgrading some mapping applications to the new 3.1 formate, however I keep getting the following error with one of the maps.

Application upgrade failed: Cannot move C:\Data\Website\flexviewers\MCPD_beta. Please make sure no files are open.

Any clues as to why?

The original map was built with the application builder, then modified outside of the software with XML Notepad.

Haskett