I have just realised that since installing this Firmware update that my Time Machine has not achieved one succesful back up although it did not issue any warnings in this regard until yesterday when I was told it had not backed up in 126 days!
Looking through the forums I see that this Firmware update has caused other issues for users with Time Capsules or Airport Extremes. Is Apple aware of this and if so what are they doing about it? as 7.6 purportedly fixes a serious security issue with earlier versions. They should by now have updated this with a fix to the issues it is creating.