>See if he can test with real-time antivirus scanning disabled.
>
>If that's not it ISTR Dragan started a thread a little while ago with a similar issue. I think judicious use of DOEVENTS was suggested, I don't know if that was the final solution.
>
>This application has run flawlessly since 2006. These problems just started to occur after he upgraded from Windows XP to Windows 7.

In addition to Dragan's explanation, if weird stuff is going on, testing with real-time AV disabled should ALWAYS be the first thing you try.

For example, at one client, sometime overnight between March 12 and March 13 a Trend WFBS update caused Windows 7 computers to no longer be able to connect to a SQL server. XP machines/Terminal Server 2003 sessions still could. The problem was Trend on the SQL Server machine.

Antivirus is so invasive and affects so many facets of computer operation that ruling it out during troubleshooting is pretty much a mandatory first step.