Hmm. Me too.
Downloaded the VDP appliance ova multiple different times. Didn't help.
Different browsers didn't help.
Fiddled around with ovftool, but that never could make a good ova again.
What did finally work is on the VMware downloads page, don't click the regular download link "Download Now" but instead use the smaller link "Download Manager". This fires up a special downloader web page. The appliance ova I got by doing that worked first time, no problems.
I guess I really was getting mangled ovas when using the regular link.
Cheers!