In Gmail all contacts got disappeared in the address book

Hi everybody,
I am using Gmail frequently. Sending mails, chatting, etc.. There was no problem with it until yesterday.
But yesterday I tried to send an email to my friends, but the email addresses are not coming which are already saved. I opened my Address Book and wondered that no contacts are present. I never delete any contacts. I am not sure how all the contacts got deleted.
What's going wrong here? Anybody faced the same issue before? Please suggest me how can I get all my contacts back? Your ideas and suggestions will be much appreciated. Thanks a lot in Advance!
