I imported a custom fixture and anytime I select the fixture and click on Preset Manager the program says invalid arguement and it crashes so hard I have to restart the computer.

Which version are you running? and did you download it from the website or the disc it came with? also was this on demo mode or USB mode? Let me know. thanks.
Sincerely,

James,
Downloaded program from website today. In USB mode. If you want me to send you the profile I can, email me at steve "at" stephenshaw "dot" "com"

I'm running latest MyDMX(same as from web site) and I am unable to replicate this issue, with or without the dongle plugged in. Took me a bit to figure out how to be able to access "preset" mode(was easier than I thought). Two fixtures used a profiles I had to make. The rest are ADJ fixtures, no tweaks needed. Worked fine.

What's your computer specs, OS, Service pack, memory, storage(space available as well). Latest updates? Using a broadband router on your internet connection?