It happened only twice to me with the network disconnect. I can't reproduce this when i'm trying, it only happenes in real life usage.. What about sleep and wake? Our new machines with Windows 7 have very low sleep time setting (30 minutes on AC). So for some users their PCs are going to sleep very often and they find freezed Spark every time they come back. I have my sleep time increased to few hours, so i've never experienced this myslef. Also i think thei PCs are losing network when going to sleep.
I'm not using igniterealtime server and i can't provide a test account. We use Openfire 3.8.2.