Check this Apple article out -> iTunes: Advanced iTunes Store troubleshooting
These alerts occur due to timeouts or conflicts trying to write a file during download.
If you encounter this issue while while downloading Digital Copies using Windows:
If using MSCONFIG steps resolves the issue, you may want to use the System Configuration Utility to turn on the third-party System Services and Startup Items one at a time (restarting your computer after turning on the item or items) to identify which System Service or Startup Item is causing the conflict.
You can turn all of them back on by selecting the Normal Startup option under the General tab of the System Configuration Utility window, but please note that this may cause the issue to reoccur.
If you are able to isolate the issue to a particular third-party software, you may wish to contact them to let them know of the conflict.
One of the biggest offenders for iTunes conflicts is security software. You can avoid the MSCONFIG stuff by just uninstalling the security software and trying again. Then reinstall the security software later and try to set it up so it doesn't create problems for iTunes (you can do this now too).