Aircard (edge Usb Stick) Does Not Find Sim Card

Hi

I got an Infinity Aircard (from the Chinese manufacturer Sunplus) from DTAC and it works fine on the laptops of my wife and daughter, both with Windows XP. When I installed it first on my computer with Vista Home Premium, it worked until I disconnected it for the first time. When I tried to reconnected later on, the software indicated that it does not find a SIM card. Uninstalling, reinstalling, going back to a previous restore point (in Vista) does not help while the Aircard continue to work well on both XP machines. During the several attempts to reinstall the software, I can see a red window appearing in a flash to short to read what is written on it. The install log shows several lines with failed EstonInstED.exe processes.

Could someone help? Thanks>