Please post screen shots (see sig link with regards to posting images) of your error, or describe the error message.
If you receive the buffer error, please try the following
1. Restart the system before executing the upgrade
2. Set the JumboFrames to 1500
3. Disable all other services, such as Web, Php, MySQL, FTP, Multimedia Streaming, iTunes
4. If you are using 3rd party software, disable or remove it from the Synology system before executing the upgrade.
5. Use Firefox 2 or IE7 to execute your upgrade
5a. Safari 3x cannot upgrade firmware versions running firmware 590 or older
If attempting to redownload the file, and it is slow from the Synology HQ servers, please look at the mirror
Hope this helps