None of the video player is playing any formats. The flowplayer says stream not found.

Did you try the right formats with the right codecs and the right settings? Also again what theme? Note that the player don't work in some third party themes that display the images via JavaScript. Like for example zpGalleriffic.

Flowplayer3 is pure flash so it only plays what Flash can. jPlayer being html5 with flash fallback requires specific files mandantory and others optionally.

Given that you didn't get the addthis stuff running it still might be a JS conflict.

I was checking gjr's website and found that it doesnt support "addthis stuff" yet many say its working for them. I dont know how. I am still using the masonry theme and it seems its a lot different in actual use than the snaps displayed on the website. Btw I am using mp4 format in flowplayer.

note:i havent received any reply from gjr keeping in mind; "he may be off for his vacations"..

Yes, but mp4 is not a format but a container. You need to make sure the codec within are the right ones. Flash does not play everything and not everything with all settings. It may fail with of ratios or other off the "standard" codec settings:
http://flash.flowplayer.org
http://helpx.adobe.com/flash/kb/supported-codecs-flash-player.html

Note: that the flowplayer plugin will go unsupported with the coming 1.4.5 release. jPlayer will be the only official player then.

As for jplayer it doesnt even show me any error hints and neither plays the clip.

Error logs on the server? The error log of the browser? Tried another browser? Tried official theme? Did you check the encoding?

Sorry, without more info we really cannot help.

No error logs anywhere. I tried an flv file and it worked with flowplayer whereas when i tried to play that same file with jplayer it didnt play. even mp3 files are not playing in any of the players. Both players shows connecting device dialog box and then fails.

Ok, it is working for me in Safari and Firefox (so flash and html5):
http://zenphoto.maltem.de/Test/philbert.mp4.html
http://zenphoto.maltem.de/Test/Zenpage-Teaser6.flv.html
(Note that is a 1.4.5 build)

Something must be different on your end given your other issues. Especially if those two links don't work for you as well.

Flv is working for me too but not the mp4 and mp3. What might be the possible reasons??

On my test site? (Note, right now jplayer is not enabled anymore but another experimental one).

As said browser (you still didn't say which it fails since that makes a difference), outdated Flash, wrong codecs, ratios, codec settings. It might also be that your server just does not recognize them, then you have to enable them via htaccess
http://www.jplayer.org/latest/developer-guide/#jPlayer-server-response
http://www.jplayer.org/latest/developer-guide/#jPlayer-media-encoding