I've done some research into this and it appears to be a bug in Firefox 19. Here's what we know:
- It only manifests in Firefox 19 on OS X
- It is related to the use of the CSS3 transform-3d property (which we use for other things)
Unfortunately, this is a particularly nasty bug because users have no way to knowing it's coming and when most other sites work perfectly fine, they usually assume that the bug is with your app.
It's worth pointing out that:
- Firefox 18 does not exhibit this behavior
- Firefox 20 (now in beta) does not exhibit this behavior (Due April 1, 2013)
The pain regarding this bug should only last a couple more weeks as Firefox 20 should run perfectly fine on any system that supports Firefox 19.
For those of you that want to be able to detect Firefox 19 in your apps (in case you want to warn your users), you can put this code in the Session.Open event handler:
If Session.Platform = WebSession.PlatformType.Macintosh and _
Session.Browser = WebSession.BrowserType.Firefox and _
CDbl(NthField(Session.BrowserVersion,".",1)) = 19 then
MsgBox("Please upgrade your browser to Firefox 20")