Your help with Gmail please

I'm really at a loss to create my email, calendar and contacts.
I've a company email (be***.com but working under gmail) and I'm not be able to configurate it neiver with active sync nor with gmail.
Keep on receiving an error telling me that access configuration of IMAP are changed: Error: Your login information for IMAP server has changed or is incorrect. Please check your account settings.
I?m driving crazy :(