The behaviour of fennec changed, so, when you open the browser, it shows the awesomescreen (the one with awesomebar suggestions and search engines) rather than a blank page. This means that now, on weave firstrun, the user doesn't see the weave firstrun page, even though it's there, under the awesomescreen.
I'm not sure this is a Weave bug, so much as a Fennec bug. It seems that if something tries to open a page, the awesomescreen should not be shown or should be rolled up automatically. Making every extension with a firstrun implement a workaround seems... not right.
Opened the related fennec bug here: bug 531071
http://hg.mozilla.org/labs/weave/rev/f7b6b33e94aa Use BrowserUI.newTab instead of Browser.addTab so that awesomescreen gets hidden if open when creating a new tab. Not quite totally fixed as bug 531071 is still open, but it should be fixed when that lands.
http://hg.mozilla.org/labs/weave/rev/35615ad234aa Use the UIReady event to start loading weave but wrap some stuff in timeout 0s to let stuff open.
Are you sure this actually works? I am hitting the same issue with Adblock Plus. In my tests delaying from the UIReady event is no better than delaying from the load event. However, window.setTimeout() changes that delay into 10ms (because it won't accept anything below 10ms) and that will do most of the time - but sometimes the tab will still be opened too early.
Wladimir, what are you testing on? It seems to be working for me on N900 and OS X builds since 1.0pre6 builds ~12/4
I am testing on Windows 7, don't have a device to test with.
Oh, and it is a 20091213011529 nightly build.