Did you uninstall your Reliance Net Connect Software & Rebooted & then reinstalled the software before attempting to update drivers in Device Manager. It is necessary to uninstall the previous install, then reboot and then reinstall the software.
I am not speculating here. I also own the Same Reliance Broadband+ Modem and have faced the same problem on my Laptop with Windows XP installed as well as Desktop with Windows 7 RC installed. In my case I was able to solve my problem by talking the exact steps I have posted. (In windows XP, I have to manually update drivers from Device Manager after reinstalling the Reliance Net connect Software, However in Windows 7 it automatically updated the drivers)
If the above steps taken properly did not solve your problem then I guess either install your OS from scratch or if you have backup (Disk Image) of your system just before your problem occurred then you can restore that.
I believe this post will make thing more clear to you.