Depends... Activesync has to work for My Mobiler to work
AFAIK... Is activesync working? If it is, try closing the PC side of My Mobiler completely, then restart My Mobiler...
If activesync isn't working, its probably the Advanced USB Networking option on the PPC that needs to be turned off... I don't know a way to change this (with a broken screen) short of flashing the phone with the option turned off in the ROM...