Hope this will solve some folks a bit of time and pain. 

Issue:
I recently had to bring one my core laptops (a Lenovo ThinkPad T60p) to Windows Seven.
I'm running Windows Seven Enterprise 64Bit Ver. 6.1 Build 7000 on it, but I found that the Tru_Install application corrupted my system USB drivers. 
I had to remove the Tru_Install application and the modem drivers, using "Programs and Features", to get my USB Drivers going again. (After a reboot, of course.) This little gem of a 3G wireless card is key to my internet mobility while on site with customers, etc. So not being able to use it really is not an option for me.  

Solution: 
I found if you go to the Sierra Wireless site, and select your carrier (in my case AT&T) and the model (USB Connect 881), you can download the latest "3G Watcher" connectivity software.
(Details: Filename: 3G_Watcher_Generic.msi;Version Info: Build 1822, 3GWatcher_R3.0.0.9_Build1822, DriverInstaller_Build 1818, GPS_Monitor Build1805, TRU_Updater_MSM B1819, TRU_Install_MSM B1816)

I ran an adminstrative install with Vista Compatability, rebooted, and viola, it detected and connected without any USB corruption.
I ran a speed test (speedtest.net), and I'm hitting about 1300-1600kbps download speeds, which seems a bit faster than the original Tru_Install drivers too.

Have fun!