Don't ask me how I triggered that one. Hadn't watched the error console, and there it was: Error: strands is not defined Source file: chrome://snowl/content/strands.js Line: 96
I saw this recently when I subscribed to Planet Mozilla while the list view was open. It looked like it was happening once for each message added.
in 0.3pre, list view is rebuilt on each new message addition (so there's a nice effect of messages popping in). the onMessageAdded observer in a setTimeout of 30 will throw a NOT INITIALIZED and 'strands is not defined' (for this feed and not others interestingly) but all is fine with a value of 100. marking fixed, please reopen if noticed with other feeds.
real reason is missing remove observers..