No network (and internet) access with a non-dsl modem !

Under Windows7 RC 7100 with a modem (Nokia N91, with pcsuite driver last version), the internet connection worked well at the beginning, and after a few days, without changing anything, now it always says "no network access", with the yellow triangle.
I'm in the African bush without any local help but crocodiles for suicide in case I can't solve the issue with you…
All troubleshootings have not detected any issue.
The modem is still connecting to the computer (Dell studio 17), IPs are appearing, but "no network access".
On another computer under xp, the internet access is working fine.
I have already:
- unticked the IPv6
- switched off the other network cards (ethernet and wireless) in order to avoid conflicts
- switched off the windows firewall
- rebooted
- tried public and office networks (home network impossible without IPv6)

Please help!
Thks in advance.

the Nokia your tethering for Internet access, right? Does the pc driver suite offer a Vista driver?. Also have you looked into drivers that are compatible for Nokia

Sorry I was nos clear enough:
The PC is a Dell Studio 17, 64bits,
The Nokia modem driver is called pcsuite (last version may 2009).
That modem is connected to the computer, but tthe network access is denied.

After 4 days, yesterday I have tried to enter (in the modem details) 2 fix public DNS, and until now, the connection is restored.
fine !
I have no explanation why Windows7 made this breakdown without me touching anything.

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