Unfortunately I cannot tell you what is your problem, but I experienced a trouble with serial link with older versions, I've had to search through incredibly unfriendly page of PEmicro to get latest version of FW for PElink, because there was a buggy version on FS page. I checked my K60 tower and it is running on ver. 30.7 and it is working.
Maybe clean up of different versions and installing latest support package for PEmicro could help.