I've noticed recently (last couple weeks, approximately) that I'll be typing along on a post for this forum, and suddenly my keystrokes aren't going to the screen. When this occurs, the text in the entry box has gone a little gray, and the flashing text cursor is gone. Clicking back into the entry box puts things back, until it happens again.

I've noticed there's some activity with the browser control buttons (Stop button lights, then dims again, progress bar appears and fills rapidly) just before this occurs, so I suspect it's related to advertisement pushes -- but I don't see why it would have just started happening; I haven't had a SeaMonkey update in much longer than I've noticed this going on, and I don't notice it on other forums I use.

I sometimes lose focus because my hand/sleeve has brushed over the touchpad on my laptop/netbook, but other than that, I've not had any bother.

Since I usually read/post from my desktop computer (which has a 102-key keyboard and separate mouse) I think it's not that. It appears to be related to something updating on the screen -- possibly the shoutbox, which updates more frequently than the ads. I don't have a problem with the updates, whatever it is -- but failing to return focus to its prior state is a bug.

Must be the shoutbox indeed. You could try clicking this: index.php?mobile=mobile and see if it still persists.

The issue with the mobile version is it's lightened so much to make it compatible with older phones etc. that it's hard to use from a real keyboard and screen. Might make a useful test whether it's shoutbox doing it, but I'm now confident it is -- it's regular as clockwork (just did it again).