I can confirm that I've got similar behaviour as well. Not sure whether it was standalone or VSTi. In the latter case it could be VST issue, where the Enter key is dispatched to the sequencer, not to the MMV.
Actually I wouldn't mind keyboard input being dispatched to the sequencer, I hate plugins who seize keyboard input in Logic, I use Logic keyboard shortcuts a lot. Though if it happened during the preset name editing only it would be OK for me.
The workaround which always has been working for me is instead of pressing Enter at the end of the preset name input, just click with the mouse somewhere outside the input field.
Best regards,
Dr Sync