OneNote: syncing failed

I love Microsoft OneNote 2010. By placing a notebook on SkyDrive, multiple devices can share and synchronize that notebook. It is a great convenience; however, it would be more if only OneNote did not fail to sync so often.

In my case, errors went as such.

In English, the messages are

• OneNote cannot sync changes in this notebook because WebDAV support is not enabled on your computer. (Error code: 0xE0000784)
• OneNote cannot sync this notebook because the network is disconnected or the network location is not available. (Error code: 0xE4010641)

Come on, network IS working, firefox is showing webpages correctly (even SkyDrive pages!). And you OneNote showed good syncing yesterday...

After a few months of such trouble, during when syncs succeeded or failed in a seemingly random manner, I finally figured out (so I think) the reason and solution. Look at this:

With a check on Internet Explorer's menu File->Work offline, it seems that OneNote would not connect to the internet. By putting off the check, sync succeeded easily.

I hope someday those error messages also show us solutions clearly, or, IE's menu doesn't cause unexpected influences on other applications.