Comment 6 for bug 1390663

After much digging, we believe we found the issue.

There's a deadlock in the client/session interface, triggered by network state flapping. While it happens readily on the emulator and almost not at all on mobile, it's a real issue: any situation where the network's state changes quicker than the connection dance takes (which can be several seconds) will likely trigger it.

Setting to critical, and aiming for RTM.