Well I can't off any insight *yet* as my Hitachi paitently waiting for me at home. However, I'll be home visiting the family and will hook up mine then (february 1st) If you've gotten no feed back by then, I'll offer what I can.
As an aside, I have previously run a Leeson VFD which did not have any of the symptoms you describe. I too had my shaft turned down (the electrical supplier did it for me for 20 bucks)
as for the start up display, have you read (a dumb question but we ARE male and typically disregard instructions) the manual. On power up it states the display should read 0.00 after runing through a display test pattern. Doesn't really mention an "H" I'll re-read and post if I have an insight.
This manual has a couple of revisions I found on the Hitachi web page, mabye worth a look see.
good luck and I'll post up again, when i get mine runing.
peace
9 1/2
B.C.I.T. Machinist CNC