It would help us diagnose your issue if you told us exactly what command you typed to try and flash boot.img, the error you reporting doesn't sound quite right.
P.s. after reading your post again it would also seam to me you didn't do enough reading before jumping in to making changes to your phone.
Sent from my GT-I9505 using xda app-developers app
Update: 17th november 2013
Samsung G S4 stock BMG4 + root
with cf-auto root + philz recovery.
HTC Desire HD
(Hboot 2.00.0029 AND S-OFF)
SVHD V 2.1.0
Retired HTC Legend