Invisible tooltips

I recently installed Linux (Mandriva 2009.1) on a new PC and moved our home directories over to it so we’d keep our settings, email, etc.  When I did this, everything mainly worked fine, except that the tooltips (if that’s what they’re called) when I hover over an item on the task bar showed up with black text on black background, something like this (simulated ’cause I didn’t take a screenshot at the time):


My wife’s desktop looked fine, so I figured it was some setting of mine rather than a bug in Mandriva or KDE 4.

It turned out all I needed to do was right-click the desktop and pick Appearance Settings:


and then choose Aya (or Oxygen):


Now the tooltip text is visible:


Rabbit trails (for those interested in how the solution was found)

I had fiddled with Configure Your Desktop -> Colors, but nothing seemed to have an effect on the taskbar’s colors.  I had recently read about something called “plasma” in KDE 4, which the taskbar is maybe part of.  I thought maybe the plasma stuff has its own color scheme, separate from generic tooltips.  Browsing through the search results from googling mandriva plasma colour settings, I found this article, which took me to a settings area I’d never been to before: Configure Your Desktop -> Advanced -> Desktop Theme Details.  I couldn’t at first figure out what to do in here, but when I changed a setting and clicked Apply, I got this dialog:


“Open the desktop Appearance Settings”… hmm… that got me exploring around (I went first to Configure Your Desktop but couldn’t find the setting, so I right-clicked on an empty area of the desktop and got the context menu, chose Appearance Settings, and picked a theme (the theme was blank when I first went there).  Fixed!