i just bought the ht-c555 and i am having problems with the upscaling too.
since my tv does not support bd wise... i change the resolution manually... but changing it from 576 to 720 to 1080i to 1080p doesn't seem to do a thing!!!! i played the same dvd to my ps3 which has upscaling and it did upscale it...

i m starting to think the dvd player doesn't provide upscaling.