tool controls bar width is 1/4 of total screen width

You have enabled an experimental feature in the preferences which allows to attach the tool controls bar vertically (see the tooltip).

Please uncheck
File > Inkscape Preferences > Interface > Enable dynamic layout for incomplete sections
and restart Inkscape.

This is part of the on-going work on the 'Adaptive UI':
<http://wiki.inkscape.org/wiki/index.php/Release_notes/0.48#Adaptive_UI>

Reproduced with Inkscape 0.48.0 r9654 on OS X 10.5.8

IMHO this option should be hidden (without GUI) in the release version.

Ditto. In addition to breaking the GUI on some systems, the option description is incomprehensible unless you have read the source code.

This is fixed in r9686 in stable, I have removed the option and the code that checks it (it's always assumed to be false regardless of what is in the prefs file). Trunk still has the setting.

That change is a good work-around for 0.48, but it is only a work-around. It does not actually fix the problem, only blocks the user from making the choice that shows there is a problem.

The true fix is to correct the individual actions/widgets that push the bar to be wide so that they do not expand when placed into a vertical toolbar. Some have been corrected already, but more need to be.

Jon: Any progress on this? (in case you can't tell, I'm hitting reports marked as In Progress that haven't actually been touched in a while)

Unassigning and resetting bug status to 'Triaged' (no activity since the report was filed).

The same issue now repeats itself with the upcoming major release 0.91.

Patch to remove the option to "Enable dynamic relayout for incomplete sections" in the stable release branch for 0.91.

To be applied to <lp:inkscape/0.91.x> only, to avoid users setting a preference which breaks the tool controls bar when using the 'wide' toolbar layout in the upcoming stable release (see also recent duplicate report bug #1387151).

Committed to <lp:inkscape/0.91.x> in rev 13682.

Patch for the current stable release branch lp:inkscape/0.92.x to remove the option "Enable dynamic relayout for incomplete sections" for upcoming stable release 0.92.

Diff tested successfully with lp:inkscape/0.92.x r15094: the specific option is no longer present in the Preferences dialog; if the user had activated the setting with earlier (unstable) builds, the specific setting in the preferences file is ignored by the patched build as expected.

Committed to <lp:inkscape/0.92.x> as part of rev 15267.