How do you have the BR player connected to the receiver?
You state that you were using the Harmon Kardon DVD that came with the receiver but switched because it was not HD. Then after switching the disc, you no longer were getting 7.1 Dolby D EX. Is the new DVD a Blu-Ray disc and what audio formats does the new disc support? If you haven't changed your connections, then the new disc seems to be the only variable here to have made a difference in your audio output.
Your cable connection between the Toshiba BR player and the receiver will make a huge difference in your audio as will the actual DVD disc. You were somewhat vague in your description. Give more details please.
I just bought a new toshiba blue ray from best buy -
My current receiver is a harmon kardon, and we were using the harmon
kardon dvd that it came with, but switched due to it not being HD. So
when we changed out the dvd, I noticed were no longer getting the sound
in 7.1 dolby D EX (7.1). Any ideas as to whats wrong?
The sound is connected to the receiver via the original audio coax cable it came with.