I had the same problem. The first time I plugged it in the splash screen came up like it was supposed to. Then after I tried to upload the firmware updates the splash screen refused to come up. I had to uninstall and reinstall the SCT software on my computer before it would work properly and the software I downloaded off the SCT site did not work. I contacted Eric at ID and he sent me a link to software that worked.
Quick question, are you holding the key you have to hold while plugging it in to make it go into diagnostic mode?