A similar problem:
http://forums.wesnoth.org/viewtopic.php?f=4&t=32665

Update:

As of 1.9.0-svn (41905), the bug behaves slightly differently, and I have an additional, yet very similar, way of causing the game to explode. Before testing, make sure that your checkout of "The Silver Lands" is up-to-date.

The new way:

1. Go to scenario naught (RPG_Utils_Test).

2. Move Sorum'tar to 11,11.

3. Open the inspector and inspect the first part of the 'lore' array.

4. An error window should have popped up (in Windows).

I have attached a screenshot of said window. In addition, this appeared in stderr.txt:

terminate called after throwing an instance of 'gui2::tlayout_placement_failed'

Contents of the first part of that array (well, what is in the WML):
OMG, the cookie magister is angry!"^"Oh noez, what shall I do?"^"Oh wait, I can just eat that morbidly obese weirdo!

The same applies to the old way, except for the variable name, the contents, et cetera.

I tested this with 1016x713.

In scenario naught of my campaign, The Silver Lands, inspecting a certain variable (glyph_text) causes an assertion failure.

The variable contains the following:

_"Do you want to be healed?

This magic glyph will completely restore this unit's health, also unslowing and removing poison from it, if applicable."+"

<small><span color='{PANGO_COLOR_GRAYED}'>"+_"Note: the glyph can do this only once, and when done it will fade out."+"</span></small>"

Contents of PANGO_COLOR_GRAYED:

#808080

Details on the assertion failure:

File: src/gui/widgets/grid.cpp
Line: 519
Expression: false

Keep in mind that I use a Subversion checkout of trunk with the hidden Windows trunk builds.

To obtain The Silver Lands:

Tarball of HEAD: http://wesnoth-umc-dev.svn.sourcefo...

Subversion checkout link: http://wesnoth-umc-dev.svn.sf.net/s...

Steps to reproduce:

1. Start a new game of TSL

2. Activate debug mode and cl to scenario naught "RPG_Utils_Test"

3. Move a unit to 14,14; select either "Yes" or "No"

4. Open the gamestate inspector and click on "glyph_text"; an assertion failure should occur

This occurs in both full screen and windowed mode.