I have the EXACT same problem, down to the number of days left on my trial! The first time I tried to start Megaten, it wouldn't go past the update screen because one of the DirectX files was missing--ddraw or something like that--and I suspect that's the current issue. (I discovered this by checking the diagnostics on the megaten updater.)
The native directX seems not to have this necessary file, and I've even installed directX from a download I made a while back for Fusion (which doesn't work with Megaten) and it didn't fix the problem.
I generally have it hooked up to a windows keyboard, but not hooking it up didn't fix the problem, and neither did rebooting.