This is the most common post here.. since mountain lion .. at least 3-7 a day.
Reboot the whole network.. but restart in correct order.. modem.. router/TC .. clients 2min gap.
It should work.. but tomorrow you will need to do it again.. and always forever more.. tomorrow.
As a suggestion .. reset the TC to factory and do the setup again.
This time use SMB names.. TC, wireless and hard disk. Short, no spaces.. pure alphanumeric.. it has been helping.