Ive tested online play with these results:
You can play online with the mod on as long as a DNAS code has been inserted somehow (Same with the Matrix) However you cannot set up a ISP connection with the net adaptor cd with the mod on, it must be off. To diable it just hold start at boot and press reset once you see the disabled sign. To activate it again turn off the ps2 or put it in standby and turn it back on.
V4 MI w/500gb HD & custom HD fan
V9 CC 2.0 w/300gb HD
V4 DMS4 Pro w/250gb HD
V3 CC 2.0
V12 Modbo 745 /clear case
V0 SCPH-10000 JAP w/ DMS3