SU doesn't even show TB in the log. Only apps allowed shown are ES File Explorer, ROM Manager, Root Check Basic, Root Explorer & Voodo OTA RootKeeper.
NP here.
Check permissions on /system/bin/su maybe.
Bring up a terminal or ConnectBot in "local" mode.
The owner should be root or 0 (zero), the group should be root or 0, and the mode should be -rwsr-sr-x (octal 6755 - read/write/setuid for owner, readonly/setuid for group members like you, and readonly/execute for others)
Commands for correct permissions: