Did they install directly, how did you install them, did you have to 'fiddle' anything?, etc.
Maybe post a detailed set of actions and, if needed, ic can make it sticky for a while?
V3G, gotta say no special tricks or fiddling, just installed as normal. That is on Vista 32bit NOT 64bit
Huawei driver used (for E620) ...
http://www.huawei.com/mobileweb/en/file/download.do?f=2820&ctype=1
Novatel driver used (for EU740) ...
http://ftp.us.dell.com/comm/R129300.EXE
Since Novatel dont supply drivers directly, you need to find an OEM version. I used the DELL ones (you have to live with splash screen) for the DELL embedded 5505 module, however it looks like the package supports most Novatel cards.
Only other thing I do for safety (not sure if it makes a dif) is to insert card before loading the drivers, in this way Vista will use its own drivers for all the PCI bridge etc. devices. After that eject card, install drivers, then re-insert card.
Once install is complete, go into 'Utility/Dash' setup PIN, Network & APN and then it works as advertised. Oh one last tip, Turn off User Account Control in Control Panel->User Accounts so Vista stops bugging you about admin rights.
Thats it.