I upgraded from 2 to 3.everything downloaded accept part 1...I keep getting an error at the end of the download that say  "can't read source file " this happened three times  any Ideas ?the rest of the files seem to have downloaded fine ,its just   3. 02 SONAR X3 Producer.part1 that I am having problems with,,,thanks for any help

Some web browsers are saving people from themselves by removing the .exe from the file name so that you can't accidentally execute something you downloaded.
 
Is this happening to you? Check to see if there is a proper extension on the file.

Having a download manager can help, especially if your connection is not consistent. There was a thread a couple days ago with some helpful links. http://forum.cakewalk.com/FindPost/2927585
 
If the file still has .part on the end, it did not complete the download. A couple other things to verify is that you have enough space and not to monitor the folder it is going to during the download (windows tries to refresh the view for you, which may interfere with the writing). A Download Manager is the best thing to help you.

Antivirus or security scanner interference?

I am trying again with anti virus off,,,I deleted all the failed attempts and dont remember what the file extension was but it seemed to be two separate files in my downloads....this is a great forum...musicians aren't up at this hour .but there are still some up from yesterday

The .part file is the temporary file as it is being assembled during download... when the download completes, it will convert to the final file. If you saw both, it failed during this conversion, so could very well have been an anti-virus issue. (The .exe file you saw was probably 0 bytes as well, though listed).

it was the anti virus....thanks all
 

Yeah - this issue comes up quite often - If I recall correctly, the indication from Cakewalk to disable/suspend antivirus software is in a file that you only get to see AFTER completing the downloads.  (I am not 100% sure of which document this is in, but think it is in a read me or something like that, which is available only after the downloads).
 
Anyways, I wish that some sort of sticky post were created with these kinds of download and installation notes available PRIOR to doing the downloads and installation.  (just a thought Cakewalk folks).  Having this kind of info available up front here in the forum, and/or listed explicitly on the download page would likely save some folks a lot of time, not to mention saving needless extra download requests of the Cakewalk servers (not having to repeatedly try to download entire product releases, just because folks did not know that antivirus software could mess up the downloads).
 
Glad you have it sorted out.
 
Bob Bone