Excessive Broadcast and High Collisions on 5400zl/3500yl

[Surbjeet]

Hi there,
i have a network powered by Procurve. While going through switches log, i found the following logs....
W 03/28/09 09:46:01 00564 ports: port B5 PD Invalid Signature indication.
I 03/28/09 09:44:20 00077 ports: port A7 is now off-line
I 03/28/09 09:43:37 00076 ports: port B11 is now on-line
I 03/28/09 09:43:34 00435 ports: port B11 is Blocked by STP
W 03/28/09 09:43:33 00564 ports: port B11 PD Invalid Signature indication.
W 03/28/09 09:43:32 00331 FFI: port B18-High collision or drop rate. See help.
I 03/28/09 09:43:05 00077 ports: port B11 is now off-line
I 03/28/09 09:42:39 00076 ports: port B13 is now on-line
I 03/28/09 09:42:36 00435 ports: port B13 is Blocked by STP
W 03/28/09 09:42:35 00564 ports: port B13 PD Invalid Signature indication.
I 03/28/09 09:42:18 00077 ports: port B13 is now off-line
I 03/28/09 09:41:38 00076 ports: port B18 is now on-line
W 03/28/09 09:41:15 00332 FFI: port B18-Excessive Broadcasts. See help.
W 03/28/09 09:41:03 00564 ports: port B18 PD Invalid Signature indication.
I 03/28/09 09:41:03 00435 ports: port B18 is Blocked by STP
I 03/28/09 09:40:45 00077 ports: port B18 is now off-line
I 03/28/09 09:38:23 00076 ports: port B23 is now on-line
I 03/28/09 09:38:20 00435 ports: port B23 is Blocked by STP
W 03/28/09 09:38:19 00564 ports: port B23 PD Invalid Signature indication.

What are these Excessive Broadcast and High Collisions? Can i get ride of these logs? It is really serious? I am using Firmware K13.25 for all the switches and MSTP configured with two instance in load balancing manner.

Even for the port showing STP off-line and online for all the switches. May be because i am not using Spanning-Tree Admin-Edge-Port for the edge ports. The reason i am not enabling Admin-Edge-Port, that what if someone make loop in the network using Edge ports.

Kindly suggest.