It seems from this linkhttp://mxhaard.free.fr/spca5xx.html
that the 420 requires the spca5xx/LE driver.
I am not at all familiar with the present state of such drivers, but do note that there is no specific driver module of that name in my install.
I would suggest the following .....
unload ALL drivers related to spca ..... use lsmod | grep spca
to find those loaded, and then unload them, checking with the previous command to ensure they have all been unloaded.
You need to do this with the camera unplugged.
When they are cleared, plug in the 420 and in a terminal dodmesg
Copy and paste the last number of lines in your next post ..... those that refer to the camera.
I am interested to see if the 'sunplus' driver gets loaded automatically or if you have to load a specific driver module.
Checking with lsmod | grep spca
should show it if loaded.
For most webcams of that era I have found the stv06xx driver to be the one to use. You might try that one if all else fails ...EDIT
Rereading things it seems the SUnplus driver is the correct one for you camera ..... which might indicate that the apps you used are failing to display it properly.
In addition to the above I have had very little success using the webcam apps you mentioned above ..... getting no display, distorted or 'greened-out' display etc.
I have now resorted to checking all webcams using the settings section of Kopete ...... I don't use the app for anything else except checking webcams
I also check webcams using VLC ..... Capture Device ...... and if one camera attached the device is usually /dev/video0
I am not at all sure any of the above will be useful ....... but it does appear that either the apps you have tried are not displaying properly using the 'sunplus' driver, or else that driver is not the correct one for the camera.
One last question ...... is there anything that needs to be done to switch the camera from 'camera' mode to 'webcam' mode?
Just asking, as I have never had one of those that I recall EDIT
Of course it may be that the correct driver for that camera is not presently available in PCLOS That could be rectified if we know for sure which driver is the correct one ......