I have upgraded from 4.9 to 4.10.1 and the blur effect
is not used any more for popups and tooltips but for
panels is working ok..

I am using NVidia GeForce 9300M GS, with proprietary drivers...

Support Information from KWin:
==========================

Version
=======
KWin version: 4.10.1
KDE SC version (runtime): 4.10.1 "release 552"
KDE SC version (compile): 4.10.1 "release 552"
Qt Version: 4.8.4

Options
=======
focusPolicy: 0
nextFocusPrefersMouse: false
clickRaise: true
autoRaise: false
autoRaiseInterval: 0
delayFocusInterval: 0
shadeHover: false
shadeHoverInterval: 250
separateScreenFocus: false
activeMouseScreen: false
placement: 4
focusPolicyIsReasonable: true
borderSnapZone: 10
windowSnapZone: 10
centerSnapZone: 0
snapOnlyWhenOverlapping: false
showDesktopIsMinimizeAll: false
rollOverDesktops: true
focusStealingPreventionLevel: 1
legacyFullscreenSupport: false
operationTitlebarDblClick: 
commandActiveTitlebar1: 0
commandActiveTitlebar2: 30
commandActiveTitlebar3: 2
commandInactiveTitlebar1: 4
commandInactiveTitlebar2: 30
commandInactiveTitlebar3: 2
commandWindow1: 7
commandWindow2: 8
commandWindow3: 8
commandWindowWheel: 31
commandAll1: 10
commandAll2: 3
commandAll3: 14
keyCmdAllModKey: 16777251
showGeometryTip: false
condensedTitle: false
electricBorders: false
electricBorderDelay: 150
electricBorderCooldown: 350
electricBorderPushbackPixels: 1
electricBorderMaximize: true
electricBorderTiling: true
electricBorderCornerRatio: 0.25
borderlessMaximizedWindows: false
killPingTimeout: 5000
hideUtilityWindowsForInactive: true
inactiveTabsSkipTaskbar: false
autogroupSimilarWindows: false
autogroupInForeground: true
compositingMode: 1
useCompositing: true
compositingInitialized: true
hiddenPreviews: 1
unredirectFullscreen: false
glSmoothScale: 2
glVSync: true
colorCorrected: false
xrenderSmoothScale: false
maxFpsInterval: 17
refreshRate: 0
vBlankTime: 6144
glDirect: true
glStrictBinding: false
glStrictBindingFollowsDriver: true
glLegacy: true

Screens
=======
Multi-Head: no
Number of Screens: 1
Screen 0 Geometry: 0,0,1680x1050

Compositing
===========
Qt Graphics System: raster
Compositing is active
Compositing Type: OpenGL
OpenGL vendor string: NVIDIA Corporation
OpenGL renderer string: GeForce 9300M GS/PCIe/SSE2
OpenGL version string: 3.3.0 NVIDIA 304.64
Driver: NVIDIA
Driver version: 304.64
GPU class: G80/G90
OpenGL version: 3.3
X server version: 1.12.3
Linux kernel version: 3.4.33
Direct rendering: yes
Requires strict binding: no
GLSL shaders:  yes
Texture NPOT support:  yes
Virtual Machine:  no
OpenGL 2 Shaders are not used. Legacy OpenGL 1.x code path is used.

Loaded Effects:
---------------
kwin4_effect_zoom
kwin4_effect_login
kwin4_effect_slidingpopups
kwin4_effect_wobblywindows
kwin4_effect_translucency
kwin4_effect_screenshot
kwin4_effect_slide
kwin4_effect_slideback
kwin4_effect_desktopgrid
kwin4_effect_magiclamp
kwin4_effect_resize
kwin4_effect_maximize
kwin4_effect_fade
kwin4_effect_sheet
kwin4_effect_dialogparent
kwin4_effect_highlightwindow
kwin4_effect_taskbarthumbnail
kwin4_effect_presentwindows
kwin4_effect_blur
kwin4_effect_logout
kwin4_effect_dashboard
kwin4_effect_startupfeedback

Currently Active Effects:
-------------------------
kwin4_effect_blur

Effect Settings:
----------------
kwin4_effect_zoom:
zoomFactor: 1.2
mousePointer: 0
mouseTracking: 0
enableFocusTracking: false
followFocus: true
focusDelay: 350
moveFactor: 20
targetZoom: 1

kwin4_effect_login:
fadeToBlack: false

kwin4_effect_slidingpopups:
fadeInTime: 250
fadeOutTime: 250

kwin4_effect_wobblywindows:
stiffness: 0.15
drag: 0.8
moveFactor: 0.1
xTesselation: 20
yTesselation: 20
minVelocity: 0
maxVelocity: 1000
stopVelocity: 0.5
minAcceleration: 0
maxAcceleration: 1000
stopAcceleration: 0.5
moveEffectEnabled: true
openEffectEnabled: false
closeEffectEnabled: false
moveWobble: true
resizeWobble: true

kwin4_effect_translucency:
decoration: 1
moveResize: 0.8
dialogs: 1
inactive: 1
comboboxPopups: 1
menus: 1
individualMenuConfig: false
dropDownMenus: 1
popupMenus: 1
tornOffMenus: 1

kwin4_effect_screenshot:

kwin4_effect_slide:

kwin4_effect_slideback:

kwin4_effect_desktopgrid:
zoomDuration: 300
border: 10
desktopNameAlignment: 0
layoutMode: 0
customLayoutRows: 2
usePresentWindows: true

kwin4_effect_magiclamp:
animationDuration: 450

kwin4_effect_resize:
textureScale: true
outline: false

kwin4_effect_maximize:

kwin4_effect_fade:

kwin4_effect_sheet:
duration: 500

kwin4_effect_dialogparent:
changeTime: 300

kwin4_effect_highlightwindow:

kwin4_effect_taskbarthumbnail:

kwin4_effect_presentwindows:
layoutMode: 0
showCaptions: true
showIcons: true
doNotCloseWindows: false
ignoreMinimized: false
accuracy: 20
fillGaps: true
fadeDuration: 150
showPanel: false
leftButtonWindow: 1
rightButtonWindow: 2
middleButtonWindow: 0
leftButtonDesktop: 2
middleButtonDesktop: 0
rightButtonDesktop: 0
dragToClose: false

kwin4_effect_blur:
blurRadius: 7
cacheTexture: true

kwin4_effect_logout:
useBlur: true

kwin4_effect_dashboard:
brightness: 0.5
saturation: 0.5
blur: false

kwin4_effect_startupfeedback:
--------------------------------------------------------

Reproducible: Always

Actual Results:  
no blurring for some windows