Here is the standard Apple answer. Which neither solves nor addresses the problem so many of us are having.
Dear Chris,
I understand that you recently upgraded to iTunes Plus and you are experiencing an error when downloading. I have confirmed that the iTunes Store is functioning and accepting connections. Therefore, the issue is likely related to your Internet connection, local network, or computer. I'm happy to provide some information that should help you connect to the iTunes Store again.
The message about connection error 3259 can appear if you are downloading multiple items. It often helps to pause the download and then download items one at a time by following these steps:
1) Open iTunes.
2) From the Store pull-down menu at the top, choose Check for Purchases.
3) Enter your account name and password, then click Check. Your purchases should begin downloading.
4) Under the STORE section on the left, click Downloads.
5) Click the Pause All button in the lower-right corner. This will temporarily pause all of your downloads.
6) To resume only one of the downloads, click the refresh button that appears to the right of one of the paused downloads.
Certain types of software can affect the way a computer sends and receives information from the Internet. Here are a few examples of these types of software:
- Firewalls
- Web accelerators
- Ad filters
- Virus protection software
If you have any of this software, you will need to configure these applications to allow iTunes to connect to the Internet. Please refer to the documentation that came with that software, and if necessary contact the software's manufacturer. You'll need to configure the software to allow these domains to send and receive data from the Internet:
phobos.apple.com
phobos.apple.com.edgesuite.net
For assistance in configuring your firewall or accelerator software, you may need to contact the manufacturer or your Internet service provider (ISP). When contacting their support representatives, it may be useful to have the following information:
"Well Known" TCP and UDP Ports Used By Apple Software Products
http://www.info.apple.com/kbnum/n106439
The following article helps Windows users pinpoint software conflicts that could cause the error:
Using MSCONFIG to troubleshoot conflicts in Windows
http://www.info.apple.com/kbnum/n302538
Once you have managed to allow access to iTunes through other software, please follow these instructions:
1) Sign out of the iTunes Store.
2) Quit the iTunes application.
3) Restart your computer.
4) Open iTunes.
5) From the Store pull-down menu at the top, choose Check for Purchases (if you're unable to upgrade and are using iTunes 6 or earlier, you'll find this option in the Advanced menu).
If you can't find this option, you can also click this link to do the same thing:
https://phobos.apple.com/WebObjects/MZFinance.woa/wa/checkForPurchases
6) Enter your account name and password, then click Check. The missing item should begin downloading and appear in your Purchased playlist. If the issue persists, please include this information in your reply:
- The name of your Internet service provider (ISP)
- The type of Internet connection (such as dial-up, cable modem, or DSL)
- Any troubleshooting steps you may have taken
- Any error messages you may have received
Apple Discussions are another source of information about iTunes, where everyone from new users to professionals can interact and share their knowledge and experiences. You may find another user with the same operating system or ISP that may be able to help resolve this issue. You can find the iTunes discussions group at:
http://discussions.info.apple.com/itunes
If you are using a dial-up connection, you might consider downloading your purchases over a broadband connection, if you have access to one.
I hope this information has been helpful. Thank you for shopping at the iTunes Store. Have a great day!
Sincerely,
Matt
iTunes Store Customer Support
http://www.apple.com/support/itunes/ww
Customer First Name : Chris
Customer Last Name : Oldfield
Web Order # :
Support Subject : Download
Sub Issue : Incomplete download
Platform : Windows Vista
Error Code :
Other Error :
Comments:
Using 7.2, upgraded 200+ tunes to "plus". Most Downloads fail, error 3529 - some have downloaded (after many tries).
No history of this problem with previous versions of iTunes.
Rebooted, restarted wireless router, disabled all progs except iTunes, disabled Vista firewall, etc. problems persist.
TrackID: 3822965
Thinkpad T60p Windows Vista 
