This rate-limited message indicates that a transmit queue and traffic on a port is blocked or limited for reasons other than being "paused". You may see the blocked transmit queue message if the supervisor engine is not able to send packets to the switching module because it received a busy bit from the switching module. A hardware failure or a speed/duplex mismatch can cause this problem.
Recommended Action:
Configure both sides of the link to autonegotiate for speed and duplex. Issue the shut/no shut command to recover the port. If the problem persists, move the connected device to another port and see if the problem happens there. If neither of these solves the problem, issue the hw-module reset command in order to reboot the switch and reset the line card.
What platform and IOS version are you observing this on?
