Your downloads on the Lion system are being corrupted. A media player will be able to play the files because a missing frame here and there isn't important and you won't see it. Extraction programs to the contrary check their archives for (CRC) errors.

Rapidshare files can be checked (MD5 check) but other hosts don't provide the necessary information. That's why they are only detected when you use an extraction program.

The cause of the corruption can be the file or the host, but it's unlikely because you've the problem with big files from different hosts. The most likely reasons are :-

1) You're using too many connections. Reduce the Max.Con. setting (bottom right corner of jD window) to 1. Reset the affected links.

2) Software on your computer that interferes with the downloading process. Please allow java and javaw in your firewall and virus software. Disable (or un-install) the html/web download scanner in your virus software.

3) Hard disk problems; I would recommend doing a disk check.

4) A faulty component (cable, router, modem, etc.) in your network. Check all your equipment and cable connectors or replace cables.

5) A bad Internet connection. If you've the same problem with other computers, contact your ISP.