Hello!
A few days ago everything was working fine, I could watch movies, using x11/xv video output, fullscreen, just perfect... But yesterday I tried to install fedora core 3 and didn't like it at all, so I returned to slack (yep, reinstalled the system). I left my home partition untouched so it was very easy to retrieve the system. Nevertheless, now I've a great problem with MPlayer - x11/xv don't work at all, I can still use -vo x11, but without fullscreen, and zoom/vm don't work. Why is it so, that there is now error while opening x11/xv device, when there wasn't such error just a day ago? I've done X -configure correctly, I think. At least my video driver *was* recognized.

What video driver do you use ? vesa ? (look at xorg.conf) Also did you set your monitor resolution
(again in /etc/X11/xorg.conf) Are you a member of video group ?

This is what I have under "device" section in xorg.conf (it was detected by X -configure):
...
Identifier "Card0"
Driver "savage"
VendorName "S3 Inc."
BoardName "86C380 [ProSavageDDR K4M266]
BusID "PCI:1:0:0"

And here's my "screen" section:
Section "Screen"
Identifier "Screen0"
Device "Card0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Viewport 0 0
Depth 1
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 4
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 8
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 15
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 16
EndSubSection
SubSection "Display"
Viewport 0 0
Depth 24
EndSubSection
EndSection

I've also just added the name of the user to the /etc/group :
video::18:raffi

It doesn't help.

Try add a line between each Viewport and Depth lines of each SubSection "Display" like :

...
Subsection "Display"
Depth 8
Modes "1280x1024" "1024x768" "800x600" "768x576" "640x480"
ViewPort 0 0
EndSubsection
...

I did what you said, so that it looks now just like that:

Section "Screen"
Identifier "Screen0"
Device "Card0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Depth 1
Modes "1024x768" "800x600" "640x480"
Viewport 0 0
EndSubSection
SubSection "Display"
Depth 4
Modes "1024x768" "800x600" "640x480"
Viewport 0 0
EndSubSection
SubSection "Display"
Depth 8
Modes "1024x768" "800x600" "640x480"
Viewport 0 0
EndSubSection
SubSection "Display"
Depth 15
Modes "1024x768" "800x600" "640x480"
Viewport 0 0
EndSubSection
SubSection "Display"
Depth 16
Modes "1024x768" "800x600" "640x480"
Viewport 0 0
EndSubSection
SubSection "Display"
Depth 24
Modes "1024x768" "800x600" "640x480"
Viewport 0 0
EndSubSection
EndSection

Unfortunately, it still does no good Any other ideas?

Ok! I've just managed to do it! It seems, that my HorizSync value was wrong. I've been googling for it for quite a long time (hp pavilion zt1170 laptop), but with no results. After all, I started picking up values randomly, and eventually got the correct one! Anyway, thanks for advice!