Many thanks for your post and apologies for inconvenience caused.
It looks as though a file called LinqBridge.dll couldn't be loaded or found on your system.
You can find the LinqBridge file in the installation folder for SQL Compare or Data Compare or SQL Doc, if you have these installed, please copy the DLL to c:\\program files (x86)\\red gate\\sql prompt 5.
If you do not have any of the above products you can obtain a copy of the file from here
Unzip the downloaded file, locate the dll file and copy it to the SQL Prompt install folder.
This should hopefully resolve the error but if not let me know.