Comment 1 for bug 574157

I'm affected by this too. Just to be explicit, here are repro steps:

g++ -ggdb -Wall -Werror -o bug1 bug1.cpp # I'll attach that in a second
ddd ./bug1
View Menu -> ensure" Data Window" is checked
b alter_list
r
# wait for breakpoint to be hit
In ddd source window, right-click on the "list" parameter to function alter_list(), and select "Display list"
Now, go to the data window, right-click on the graphic view of "list". ddd will hang, and mouse will be grabbed into the data window.

Note: You can recover from this without killing X by:
CTRL-ALT-F2 to switch to a text console
Log in
kill `pidof ddd`
CTRL-ALT-F<<n>> to switch back to X