If you already didn't, check out my new
Exact Audio Copy and LAME Quickstart Manual. Thuis manual guides you through the installation and configuration of EAC in about 10 minutes.
Anyway, your problem is most likely an incorrect command-line. You might (or might not) have noticed the %s and %d in the command line to LAME in EAC. They were not present in older versions of EAC and are nowhere described in the LAME manual. The %s and %d stand for source and destination file respectively. If you choose the "User Defined Encoder" "Parameter passing scheme" in EAC instead of the "LAME MP Encoder", it's necessary for EAC to know where LAME accepts the source and destination file in the command line. Hence the %s and %d. If you select "LAME MP Encoder" from the "Parameter passing scheme" dropdown box you may omit the %s and %d.