My wife was having this issue a few weeks ago. She was trying to upload a document from her work computer and it was hit or miss; sometimes it would work, others it wouldn't.

Check your security settings and turn off "Use full security sessions". My brother & myself found this to be the cause of our upload failures.

Well not sure what changed, I turned on full security sessions thinking that maybe HTTPS would pass through the corporate proxy better than regular HTTP and I also turned on SSH.

For now it's working but I don't have a good explanation and it's still frustrating. I suspect something to do with HTTP Proxy.

My advice/request to POGOPLUG, enable Proxy support in the desktop apps. Most people behind corporate firewalls will require this.

UPDATE:Definitely the HTTPS vs HTTP (full security session) settings for me, I tired turning full security off and my problem re-appeared, turned it back on and everything is fine.

Problem being that none of my uploaded pictures will preview or show with full security session turned on so now I have to turn security sessions off when done uploading.

A pain but better than not working at all.