Having run into this similar type of issue more and more frequently in recent times, it is becoming increasingly obvious that Office 2003 or 2007 wont be 'fixed'to better operate on Windows 7.
Everything I have read in the last 2 hours regarding this type of issue, the answers are saying Úpgrade to 2010.
Microsoft dont seem to be acknowledging the issue, and are even less likely to do anything about it given their support timelines for this program.
In dealing with this with 2 clients recently, upgrading to 2010, while opening a whole different can of worms, has at least stopped the program from experincing the 'not responding' issues.
I'd be keen to see if you get any different responses or resolutions to this.