Just to be more specific about what he means by "screwed", here's how it goes when this happens to me. I use "transparent, dark background" as my settings. When this happens, the colours seem to go to white-on-white; the background looks normal initially, but whenever I type something I get a row of white rectangles instead of any text.

When it's in that state, it also fails to refresh itself properly; any windows that were ever on top of the konsole end up staying there. I'll attach several screenshots of konsoles in this state; the error message at the start is an unrelated weirdness on my system. The third screenshot shows the "white boxes" font problem most clearly; I typed "whoami". The other two shots show what happens when you start moving windows over the messed-up konsole.

This usually resolves itself eventually if I keep trying, or set the scheme to "white on black" and then back again.

Created attachment 6358 [details]
Konsole after a lot of windows have been moved onto it

Created attachment 6359 [details]
konsole after a couple of "ls" commands

Created attachment 6360 [details]
konsole after typing "whoami"

The same problem here:
If i use my dark transparent color scheme, konsole looks weird white as if it would have been frozen.But it still reacts and i am able to set it to another scheme.

My system: 
Gentoo Linux 3.3.3-r6
Kernel 2.6.6
Framebuffer support compiled in for matrox 
(i will check it without framebuffer soon)
gcc 3.3.3

Created attachment 6363 [details]
konsole after start + resizing 

Here you can see konsole after i resized it a little bit. If i resize it over a
certain amount (not much) after started, messed transparency changes to clear
grey color.

Update:
I noticed debugmessages in console where i started kde everytime the bug appears.

kdeui (KRootPixmap): WARNING: [virtual bool KSharedpixmap::x11Event(XEvent*)] illegal selection notify event.
kdeui (KRootPixmap): WARNING: [krootpixmap.cpp:243] loading of desktop background failed.

I can confirm this bug on RedHat 9 with KDE installed from sources. 

Perhaps this helps a little bit to track down the bug:
If i don't use 'dynamic hiding' transparency works and
the bug never occurs.

I think the following bug is a duplicate of this one:
http://bugs.kde.org/show_bug.cgi?id=83475
There's another screenshot in that report.

Also, it just happened again to me; here are a few more details. After the first konsole had this problem, any other konsoles I opened also had the same problem. Then, after I set the schema to "white on black" in one of the messed-up konsoles, all konsoles I opened after that were fine again.

I can also confirm that the debug messages described in comment #7 are also present when this bug occurs for me.

I have the same problem, debian/unstble, kde-3.2.2

i've found somthing that affects this bug.

i've got tab bar and scroll bar turned off in "settings" - with these settings every so often a konsole window will display the reported problem

if i turn the tab bar on (either top or bottom) the problem does not seem to appear.

I can also confirm this, this time with Gentoo sources.

I'm using KDE 3.3 here and also have this problem, but only sometimes. I didn't have the problem in KDE 3.2.3.

i use kde 3.3.0 now and the problem is gone as far as i have tested it in the last 5 days. it works on all 3 monitors (multi-head setup w/o xinerama).

>i've got tab bar and scroll bar turned off in "settings" - with these
> settings every so often a konsole window will display the reported problem 
 
> if i turn the tab bar on (either top or bottom) the problem does not seem to
> appear. 
 
I tried this, too. I always have scrollbar and tabbar on. When I switch the tabbar off, the problem disappears, but the window will get opaque, and will not be transparent anymore! But at least I can read the output again.

Again, I cannot reproduce the malfunction. It only happens now and then.

This problem just happened to me. I was compiling wine (by hand), then I pressed the "hide tabs" button, and it did what your screen shot shows.

Created attachment 8838 [details]
Snapshot of the bug, compiling amaroK

You can reproduce this by hiding the tab while something is moving quickly on
the konsole (like a compilation)

KDe 3.4 has new code for hiding the tabbar.  This should solve these problems if they are indeed tabbar related.
If any of you can run CVS, please update and try it.  If not wait til 3.4 comes out.

*** Bug 91367 has been marked as a duplicate of this bug. ***

I'm seeing the same problem.  Bug 83475 and Bug 87462 appear to be duplicates as well.

Not only do I see this same problem, but none of the ideas listed by other people for how to fix it work for me (turning on tab bar, saving another schema as default, and then switching by hand, etc).

The only way I can get a usable konsole is to grab the lower right resize widget, shrink the window down a little bit from it's starting size of 92x36, at which point it becomes grayish (opaque) with white text.  Then I reset the schema and get a white on black window, which is acceptable, but I'd really love to have the transparency working.  It's a good thing I like konsole too much to consider switching to an inferior terminal emulator like Eterm :-)

It just occurs to me now: even if I save white-on-black as the new default, it doesn't take!  I still always start out with a broken transparent konsole which I have to fix by hand.  FWIW.

My system is KDE 3.3.2 Level "a" on SuSE 9.1 Pro on a laptop (Thinkpad 600X)

just saw that this bug is still open - didn't have any problems since about 3.4 so i mark it as resolved :)

Created attachment 36161 [details]
kcrash file of the described SIGSEGV

Sorry - attachment to wrong bugreport because the bugtracker didn't put me back to my original post :/