On the Ubuntu bug tracker, it has been reported that GEdit's UI blocks on slow I/O, causing it to appear unresponsive when performing network work.

Original report:
How to reproduce:
1. Use gedit 2.30.3 from Ubuntu 10.04.
2. Open one or more files from slow storage (e.g. sshfs over 100kbit/s connection).
3. When working, opening and storing the UI will often become unresponsive.
This will result in delayed response to clicks, scrolling and sometimes even gray out the whole window.
It is not only constrained to the current file but will affect all open tabs.

 I think gedit needs some more multi-threading, doing the blocking tasks in the background not annoying the user.