Radio UserLand customer support board are trying to find the cause for intermittent upstreaming problems.
One theory is that people who use Radio with sometimes-on, sometimes-off Internet connections are more likely to have problems publishing. If any experienced Radio users can offer some assistance on this subject, there are at least a dozen people you can help pull back from the brink of madness.
I made a post today about my Offline Toggle tool. It checks for a net connection every minute and if none is found it turns off upstreaming and sets work offline. Naturally, if it finds a valid connection it turns these things back on again. It also lets you know what it's doing in the Event's log.
I hope it helps someone.