Version:           unspecified (using KDE 4.5.0) 
OS:                Linux

Running PCLinuxOS, with an nvidia GeForce FX5200 and a Dell ST2310 1920x1080 monitor.  Desktop effects were working with the original PCLOS 2010 installation (KDE4.4).  Also worked with Mandriva 2010.0 (KDE4.3).  Stopped working when PCLOS upgraded me to KDE4.5.  Blur effect is disabled, for what it's worth.  OpenGL screensavers still work.  If I switch to Compiz on the same PCLOS install, their effects work.

Here's what I see. Screen freezes (sometimes with vertical wrap of the display - taskbar redisplayed near the top).  Mouse cursor still works.  Hovering over taskbar buttons causes the whole screen to repaint correctly along with the popup thumbnail.  So does activating the 'desktop cube'.  I.e. I'm able to see and click the 'suspend effects' button and get kwin 'working' again with effects disabled.  Clicking anything else appears to do nothing, though the screen is 'repainting' behind the scenes, and show up on the next thumbnail popup.

Anyway, I've been told on other forums that it's the fault of my 'ancient' video card, but I'd hate to think that the point release from 4.4 to 4.5 was intended to break hardware compatibility.  Elsewhere I've seen recommendations that the new blur effect causes problems, but turning that off doesn't help.

In any case, I can't upgrade my video card, since my box is PCI, and all I see available these days are PCI-Express cards.  I'd like to know whether this is considered a bug or whether I'm out of luck on my existing hardware (which otherwise performs very well).

If I drop the resolution to 1280x1024, 4.5 effects work, but I can't seem to select any other resolution - whatever I pick, X autoconfigs to 1920x1080.  Either way, dropping resolution's not a viable solution - switching to Compiz would be better than that.  Still better would be a way to disable whatever new feature is incompatible with my hardware - or maintaining a 'use 4.4 kwin' option.  Seriously, I thought the KDE4 underpinnings were intended to break compatibility upfront, but maintain it thereafter (at least within the KDE4 series).

Reproducible: Always

Steps to Reproduce:
Turn on effects using GeForce FX5200 at 1920x1080 resolution under KDE4.5.