I have encountered a similar situation and posted about it here.
Basically, the Tivo thinks there is a transfer already in progress, and the solution I have found is to reboot your entire network. This includes the Tivo(s), PC, and
router/cable modem. The trick is to not cancel any pending transfers on the Tivo with the problem and to not
restart everything at the same time. Let individual components start up and become stable before you restart the next, starting with the PC/network, and then individual Tivos last.
I have found that a pending transfer must reset something in the Tivo software upon reboot, whereas, if you don't have a pending transfer, nothing changes. This has only happened to me once, so I may have been lucky that what I did fixed my
problem, so YMMV.
There could be other reasons why this happening to you.