HP Deskjet 3820 Printer Cartridge Stalls

I recently replaced a #15 black and #78 color cartridge on my HP Deskjet
3820 printer with brand new HP cartridges. Now the printer will not work at
all. When the power is turned on the rollers spin in both directions - the
cartridges move to the left hand side of the printer and a page ejects and
then the cartridges move back to the home position. When I try the local
print test page (hold down power and press resume 4 times), the power light
just flashes continuously and the cartridges don't move at all. When I try
to print a text document, I get a mechanism error / cradle could be locked
error.

The printer is still in its first year - is it a serviceable problem?

Thanks,
Peter