Comment 6 for bug 1108045

A little update from my side. It seems like the whole issue is related to the proxy server used in the office where I work. I mentioned that I saw such an error in the proxy.log.
Today I took my office laptop at home and there was no issue. The Ubuntu One folder was synchronized without any issue.
In order to further troubleshoot this, which looks like a networking issue... How is the Ubuntu One for Windows app determining whether to use proxy or not. A bit more about my setup:
1. I use a wired connection.
2. I use a statically configured gateway to exit out of the office network, bypassing the proxy that way.
3. I use static routing for the office networks, which off course are routed through the proxy server.

I've got the impression, that with this setup Ubuntu One is still trying to exit the office network through the proxy server, even though the default gateway (statically configured) is pointing to a gateway which bypasses the proxy server.