Comment 56 for bug 276990

The backports module also solved my problem.
Before, transferring large files over the local network would crash my system within seconds. I have now been able to transfer several large files without problems. I still see error messages in dmesg, but they don't seem to cause too much trouble.

For those still experiencing problems, it might be useful to know that you can use this command to check which module is actually being used:
modinfo iwlagn|grep filename

The module in backports is in /lib/modules/2.6.27-7-generic/updates/iwlagn.ko.
If you need to find out what package the file belongs to, you can do for example
dpkg -S /lib/modules/2.6.27-7-generic/updates/iwlagn.ko