Dragging guides freezes, behaves errativally

Running Inkscape 0.48+devel on Ubuntu 12.04, recently upgraded from the stable 0.48.

Running the development version, dragging guides from rulers does not seem to function properly. There's several erratic behaviors:

- Dragging a guide from the ruler will work for a fraction of a second, and then the guide freezes in place even when the mouse keeps moving. It then disappears for a few seconds, then reappears either where it was or where the mouse stopped moving
- Shortly after creation (above), guides will sometimes randomly disappear and then reappear off-screen
- Ctrl-clicking on a guide (to delete it) does nothing, but sometimes the guide will disappear several seconds later, or if I scroll it offscreen and back
- Most of the other guide functionality doesn't seem to work: double-clicking on one doesn't open a dialog, they can't be dragged or otherwise adjusted after creation, etc.

These are completely reproducible on my machine; I don't know about others. I haven't delved into the Inkscape codebase before, but if someone can point me to places to look, I could investigate to see if it's something about my local libraries. (Since I couldn't find another instance of this bug on the boards, I assume most people don't have it.)

Thanks.