Created attachment 43527 [details] [review]
Xorg.0.log

Xorg.0.log provided.

Created attachment 43529 [details] [review]
dump lspci

Created attachment 43530 [details]
vbios

a little more description about the problem.

1. Existing for long 
   The problem has been reported from April 2010 or before, on all Linux
platform. Appears the Radeon driver has repeated EDID error and RAW dump
reported into syslog and related log files, causes log file rapidly increasing
in size of 100M per day.

2. Specific to my HW.
   The mother board ECS A740GM-M version 7.0 uses chipset AMD 740G, which
integrated ATI Radeon 2100. The chip support VGA and DVI ports, but to this
version of mother board, the manufacture only has VGA connector installed.
There no DVI port at all on this mother board.
   The Radeon driver repeatedly scans the video connectors, reports a
connection detected on DVI-1, but with invalid EDID checksum. 

3. Severity of the problem
   Since the great amount of dump to log happens in every 10 seconds, the
system suffering in obvious performance degrade. In some slower system, report
says the system appears frozen about 5 seconds in every 10 seconds.
   In non-GUI configuration, the repeated EDID error message dump into console
for every 10 seconds, makes the system hardly management.

4. Whos fault
   The board has no DVI connector at all, but the Radeon driver repeatedly find
a connection on DVI-1 port. It possibly because the manufacture does not handle
the unconnected DVI signals properly, which causes the driver keep claim
finding a monitor connected into DVI-1 port. 
   However, these repeated message were useless to ordinary end user, instead
of annoying and lower system performance. I will like rather see such error
message in log only once for every system reboot, or provide a debug switch in
xorg.conf to allow the error to be repeatedly reported (in case a debug
engineer want to on-site).  Other thought is, the driver could better to
provide option in xorg.conf to disable detect on specified video port, so the
driver will NOT to scan and detect those ports over and over again.

Is this still an issue with a newer kernel?

The problem is known in Ubuntu: see https://bugs.launchpad.net/ubuntu/+source/linux/+bug/810926.

Either upgrade your system to Ubuntu Oneiric or install the fixed kernel (with backported kernel patches) from Launchpad PPA for Ubuntu Maverick. 

Both solutions will fix the problem, as it did for the others having this special buggy chipset.

btw the Ubuntu bug has been closed with status Fix released.