welcome!
the startup error, i guess, is the same that i fixed in #239.
sadly #239 was "returned to factory" because of an heavy bug. but yes, it's about a VFS file it tries to load on startup, so you can clear it, or load/save to workaround it.
the ALT+F6 not working:
1. please, check if beside HFS.EXE you can see a file named HFS.EVENTS, and report here
2. it may be a bug, or you may have defined a bad template editor. Menu > html template > change editor
if you never used this menu, HFS should just call NOTEPAD.
If, instead, this is the problem, you can find it by using Menu > debug > show customized options
anyway, what ALT+F6 does is just to call a text editor (like notepad) on the file HFS.EVENTS
not very much, you can even do it yourself. but i would be very interested in knowing what's wrong with your HFS.
every time you save, HFS will reload the file.