I recently switch to Expression Encoder 3 - had a lot of issue with the previous MS encoder, including blue screen, multiple boot to recover. So far, i haven't got any disruption of my stream since i switched. Went out three times for about two hours of unninterupted stream.
I would recommend to switch to Expression Encoder 3 - better interface, easy to setup, and the best, it is reliable and stable. Flash encoder is nice, but you need a big machine as flash is using alot of ressources to do the same job. I have them both, and EE3 is working great without crashing my system.
I also tried Livestream channel/encoder - that one is also very reliable and adaptive (and free), but work only on their site (of course). If you have a solid 3G HSPA connection, then Livestream is a better solution to broadcast - full quality.