It does sound like a driver issue. Can the drivers be run in compatibility mode to see if it is a 64 bit issue?

A search shows quite a few with Win 7 problems ..



Have you tried Saffires suggestions and new drivers?

I found this-
Windows 7 Users:

If you were previously using a Saffire on Windows 7 utilising the Windows Legacy FireWire driver, you will need to update your Windows FireWire driver before installing this update. For more information on this, please visit the Focusrite Answerbase.


Here-
http://www.focusrite.com/support/saffire/saffire_pro_24_dsp


I do not work here, but the benefits are still awesome
Make your sound your own!