For me the problem is now solved :-)
I replaced my old, slow D-Link router with a new Net Gear one.
And I switched to the intel, open source drive, iwlwifi.
All is now working fine!
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ipw3945 Wifi connection is very slow
https://bugs.launchpad.net/bugs/103210
You received this bug
OK, spoke to soon. It's very slow again now and phones don't seem to
make any difference.
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ipw3945 Wifi connection is very slow
https://bugs.launchpad.net/bugs/103210
You received this bug notification because you are a member of Ubuntu
Bugs, which is the bug contact for Ubuntu.
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I also have a Dell Inspiron 6400 with Intel PRO/Wireless 3945ABG card
and experience the issues above.
I wonder whether it's related to interference from other devices?
I have a BT cordless phone next to the wifi router and when the phone is
off its base station wifi speeds are terrible (ping