I have heard that before in an article I read somewhere but here is some on what the big deal is.

http://www.winnetmag.com/SQLServer/Article/ArticleID/21752/21752.html

However the file is instcat.sql can also be an issue with MDAC updates on the server or the clients.

To correct you may actually want to search for all instances of instcat.sql left various installs and which every has the highest SYS_SPROC_VERSION values being inserted may be the one you want to install.

Note thou, this is not a guaranteed fix and of course you shoul have a backup of master db before you run for safety.