For non Broadcom Wifi Card users: This might break your wireless drivers.
First try if your Time Machine works without this hack!!!
- Download the IONetworkingFamily kext found here (see this thread)
- Make a copy the existing of /System/Library/Extensions/IONetworkingFamily.kext
- Install it with kextHelper
- Configure your Time Machine settings
In case you get a "The backup volume could not be found" error, do the following (found here):
- Open System Preferences.
- Choose Time Machine
- Click "Choose Backup Disk…".
- Select your backup location again
If this breaks your wifi, just reinstall the copy of IONetworkingFamily that you have made earlier (or from /Backup Extensions if not).