Ok first to clarify.The service has only over the last few months been compatible with 64 bit systems with the release of the new(yummy)player.However some games are still using the old 32bit(exent)player.The old player is not 64 bit compatible and therefore any games that use this player wont run on a 64bit system.Metaboli are in the process of repackaging the games to use the 64bit player so they will run on 64bit systems.As im sure you are aware this will take some time as the service has over 500 games
Now on to your issue.
Is your hard drive set as a c: or does it have a different label.On a default install of the player it needs to install to a c: atm.This is a known isse with metaboli and is being looked into atm.If your drive has a different label change it back to c: or create a partion and label it c:
If your harddrive is labeled as a c: them there are a few things to try
Try turning uac off this has helped some people.
Try using a different browser ie of ffox
Check both browsers to see if the yummy plugin is installed
do you have the latest flash and java as the site needs them
is your dx up to date you can get that here of it is'nthttp://dl.metaboli.fr/update/DirectX/DirectX9c.exe
I had the same issue myself earlier toady so if that does not help try the following
Close your browser
press ctrl/alt/del(xp) ctrl/alt/escape(vista)
in the applications tab highlight yproxautlaunchermain and end task also yproxmainform and end task
uninstall the player and choose to keep all games
open firefox and goto tools/addons and uninstall yummy conduit player
open ie goto tools manage addons select all addons from the drop down list.disable ieproxyform control
then goto control panel/folder options and show hidden files and folders
then goto start and search for metaboli and yummy seperatly to delete any files and folders that are left using the search function personally the only file other than the games i found was YPlayer4.ygsq.
At this stage be carefull that you dont delete any folders that contain your downloaded games otherwise you will need to download them
then run a reg and spyware sweep(i personally use advanced system care which is free and available from iobit.com)
after sweep restart and reinstall the player.
This resolved the issue for me.
Hope this helps if after trying this you still have problems repost please