It may show a connection, but many cell based internet cards time out at a low amount. They will stay "connected" but the internet will be disconected. I have experienced this with Verizon mobile hot spots, and also with Sprint PCMCIA cards.
A work around I have found is sending a constant ping that keeps the connection alive.
1.) Open Notepad
2.) Copy and paste the following into it:
Code:
ping google.com -l 20 -t
3.) Go to the file menu and save as "C:\Documents and Settings\All Users\Start Menu\Programs\Startup\keepalive.bat"
Make sure that you change the bottom box to "All Files" as opposed to "Text File"
4.) Click Save.
This will pop up a black screen on startup. It keeps sending information in small amounts over the internet to prevent it from shutting itself off.
If you don't like the window running in the background, check
this article.
Good Luck.