backup on iphone 4

hi,

when i trying to backup my phone on itunes i getting a message (it's the translation from Hebrew)

"itunes was unable to backup iphone (my iphone name) since the backup was defected or unmatched your iphone" and under this "delete the backup for this iphone and tray again",

also, the "recover from backup" button is gray and i says under this the my iphone was never backed up on my computer ever...

i can't find any solution to this problem, and i followed all the instructions on the 'resolve iOS update and restore errors in itunes' i can't backup my iphone and i can't sync him with itunes.

i will mention that i did a computer clean up with AVG software and i uninstalled har and i do have an AVG antivirus and i tried to disabled her, also got the latest Version of itunes, but still getting the same massage again...