Sidebar vanishing issue

[blackartz]

Hi there,
having just rebuilt my various sidebar widgets for the second time, I'm looking for a little insight.

After having a little trouble with the visual appearance of one of my widgets, I thought I'd see how it looked in Twentyten in case my style sheet was interfering. Having switched to this theme, the whole admin widget area seemed to grind to a halt and the page failed to load correctly. I restarted the browser and reinstated my custom theme to find all my widgets, from all my widgetised areas, had been dumped into the 'Inactive Widgets' repository, so at least all the settings were retained.

I'm just wondering if this is what you'd expect to happen when switching to twentyten? If not was this a well known hiccup or something to worry about?