If you start watching a recording and then stop watching, can you then go to the TV guide and set a recording now that the box has come out of standby.
Edited to add; have you always had this problem and if you have could it be something to do with the port forwarding problems you have posted about previously.
If your 360 is connected by ethernet cable to the hub it shouldn't be too hard to swap to router mode to rule out any possible problems with your mesh and if that doesn't help just swap back again to modem mode.
