I am using the Orange data card and it works fine on both 3G and GPRS. Probably better than the Vodafone card I used to have. The Orange software doesn't have the roaming problems that I experienced with Vodafones software.

Sounds like you have an installation problem with the software. You need to make sure you have completely removed any old software from your machine. The drivers will remain installed even if you remove the software. You should have got an external antenna with your card and this should help boost the signal.