PIXMA iP4300 will not print text on pla...

PIXMA iP4300 will not print text on plain paper but when I select High resolution paper or better it prints fine. Both Black cartridges are full. I always use Canon ink. I normally use the printer for photos (good) so did not discover this until recently. Installed newer driver V2 did not resolve. Nozzle check does not print PGBK, not even the side bars and does not do it when the default is changed to High resolution paper. Considered dry-out of cartridge but shows ink when a tissue is pressed against it. Deep cleaning of PGBK does not help. Reverted preferences to Default did not resolve. Basically when trying to print text on plain paper the page is ejected with no attempt to print. Running XP SP3