You should have tried searching the forum before posting ....
I don't promise this will work, but worth a try ....
It appears from http://support.muse.adobe.com/message/4752196 that the solution to this is to dump ADE2.0 and install the much more reliable 1.7.2.
(1.7.2 is also the solution to lots of other ADE problems)
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172
Thank you for the tip, but installing an earlier version of the program did not work either. I did search the forum before posting, and I couldn't find any solutions that would fix the problem. Regardless of what I do, it still comes up with an error when I try to download anything with a .acsm file extension. Any other suggestions?
Another thing that helps some issues is to deregister and then reregister.
ADE error messages seem a bit random sometimes, but this came up in http://forums.adobe.com/message/4740491 as a possible help for E_STREAM_ERROR
ADE sometimes gets into some half-registered limbo (according to that post it is an incompatibility between versions).
To deregister, ctrl-shift-D when in Library view.
Then restart ADE (maybe not needed) and reregister with the same id and password as before.
(Sorry, the link I gave in the earlier post was to the wrong thread.
There was a two page thread on E_STREAM_ERROR which I can't find again).