Error 526 occurs when your macro security setting in Microsoft Word prohibits the ITP/Model Development Kit from starting.

The ITP/Model Development Kit relies heavily on macros. These macros are located in the ITPMDKServer.dot template. Aia Software signed all macros in this template. This means that a solution to this problem, while keeping the security setting on high, is to trust Aia Software as a source for macros.
To add Aia Software to the trusted sources do the following:
A window will appear:

The button Enable Macros comes available.
This will add Aia Software to the list of trusted sources.