Mac peripherals forum: Time Machine Backups Failing - Disk not available

I am having problems with Time Machine Backups failing because the disk is apparently not available. I have had this Time Capsule since September, and backups worked fine for about 3 months. Then, I started seeing messages about my backup disk not being available. A restart of the MacBook generally fixes the problem, but within about 18 hours, I have the same problem.

The deterioration goes along the lines of when I am backing up wirelessly, the backup disk becomes not available. I can usually mount the disk in Finder manually and may or may not be able to convince Time Machine to do a backup. If I connect my MacBook to the Time Capsule via Ethernet, I can get backups to work just fine. If Time Machine gets stuck making the backup disk available (wirelessly), Time Machine is unable to cancel successfully, and the computer is unable to shut itself down and my only way out of this has been to press and hold the power button. Then, after a restart and about 18 hours, the cycle starts again.

Given that I don't seem to have any problems when connected to the Time Capsule by ethernet cable, this has suggested that my problem lies in the wireless network settings. At all times during my problems, my internet connectivity through wireless is fine - the MacBook just can't see the disk. I have restored the Time Capsule to default settings and reset the network settings manually but this hasn't fixed my problem. I haven't yet erased the time capsule disk, because so far I feel it is a network access problem. I have used Disk Utility to check my image and it did not report any problems.

As the Time Capsule is set up in automatic radio mode (so can run both N and G networks), I changed the setting to only broadcast a network for the G radio mode. During this period of several days, I had no backup problems. Once I switched back to the automatic setting, the dreaded cycle started again.

My Husband's MacBook is also experiencing similar problems, so I am confident it is a Time Capsule problem and not a MacBook problem. In addition, I spent a holiday at another house with a 2Tb Time Capsule (Simultaneous Dual Band) - slightly different model - and for over a week had no problems backing up to that Time Capsule.

Has anyone else seen this problem or have any suggestions?

Late 2007 MacBook, Mac OS X 10.6.2, 2Tb Time Capsule (Simultaneous Dual Band II) set in automatic radio mode.