Panasonic DMP-BD30K audio decoding problem - help!

[woodthecrab]

i recently bought this dvd player to go with my 1080P mitsubishi 57" DLP. no problems with picture via HDMI directly to TV. i have the audio hooked up to my receiver (technics sa-da15) via digital optical line. the receiver is dolby digital/dts capable and has had no problem producing 5.1 dolby digital or dts through several other dvd players, most recently an upconverting panasonic. my speakers are klipsches all the way around and have not been unhooked. they are bi-wired.

the problem: i have altered the dvd player settings as per the manual to "bitstream" with bd-video secondary audio "off " and the HDMI decactivated for audio. when i play dvd's (both blu-ray and non-blu-ray) my receiver's LCD shows the appropriate format 5.1 digital or 5.1 DTS, whichever it is set for, but it is only playing through the front speakers. the sub works on blu-ray dvds, but not on conventional dvd's. no center channel, no rears in either case. when i use the display option on the dvd remote, i get a window on the tv screen that shows me the soundtrack mode. it is always dolby digital or DTS 2.1, and it cannot be altered, even though the receiver says it's in 5.1 mode.

i'm inclined to think that the problem here is with the dvd player since the receiver, though 6 years old, has never had decoding issues before. i'm going to be pissed if i need to buy a new receiver to get the correct sound on this dvd player.

can anyone figure out anything else to try????
(btw, i did upgrade the dvd player to v. 1.3 when i received it.)

edit: also, i do have the dvd player set to multi channel mode, but when i run the test, there is no sound from any of the speakers.