I had the same problem. For some reason (this might be only with me but it worked for me), I had problems ftping into the ps2 when the elf was launched from anything other than the MC. You basically need to keep trying to connect untill it finally gives you MC access and put exectftp on the mc and boot it up from there. Once you boot it from the mc that usually solves a lot of problems. Check here for more info.
check out my tutorial at:
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Tutorial includes: MC exploit, ExectFTP, FAPLink, KeyLauncher, HDD parititions, LaunchELF, 48bit patching, skinning HDL/HDA
Message me for any additions you would like to see on the tutorial.