Okay, so I seriously don't want to necropost on this even though its close enough in respect so I'm doing the addendum as its own separate issue. This is basically here for those times when you absolutely have no way into RPGMV or whatever version is on your system, and you suspect a glitched, bricked, hostage* or otherwise borked project is to blame (and you don't want to run risk of a complete reinstall).
Anyway, for background on the macOS equivalent go to the
original post. For Windows users encountering the shutdown issue described therein, equivalency is as follows for clearing prefs. (Obviously this should be done to the point or you may brick your system because regedit. Also, Vista/7/8/10 will request confirmation to load the required interface because UAC.)
For the purpose of this subject, the path of the prefs for MV on Windows is regedit\HKEY_CURRENT_USER\Software\KADOKOWA\RPGMV and under the definition "projectFileUrl" (quotes used only for emphasis) is your most recent project. That's Command+R (the key with the flag and the letter R, macOS users on Boot Camp dual-OS as opposed to Steam will have the Apple symbol equivalent as reference which does the same thing) followed by regedit and return/enter. Again, because this specifies regedit I MUST WARN YOU ONE MORE TIME NOT TO GO MAKING A MESS and tell you politely to simply clear NOTHING but the specified datapref. It's a standard REG_SZ and should be cleared (double-click, select all and delete, OK, close regedit).
Now run RPGMV off Start, Steam etc. and you should be back in business. I'd also create a secondary project before closing so that you have a safe reference to fall back on in case this kind of thing happens again.
EDIT: Part of the reason for this post, besides the obvious issue, is the porting script can be a PAIN up "you know where" when asset migration is in order, and a botched port can nuke the destination project straight to oblivion. (Took me several tries, in fact!) Also, if you're NOT in MV and you blew up your work substitute Enterbrain\RPGxx (xx being the version, e.g. VXAce, XP) and clear the pref for LastProjectName.
* Yes, computer data
is a logistical hostage these days so be sure to have a backup.