After enabling/disabling the OSK switch a couple of times, I ended up seeing two on screen keyboards active at the same time:
- what I suppose to be the "regular" one, which takes up the whole screen width and slides in from the bottom
- an "embedded" one, which pops up chromeless and attached to the focused text field. This one looks about 500px wide and doesn't have all the keys the bigger one has, but it has a key with a keyboard icon on it, similar to the one in the bigger OSK. When I click it, an "Antler preferences" dialog popped up, and then the program to which the keyboard was attached (XChat) hang.