gmail e-mail

[sjradzik]

I have been using gmail for years to my full satisfaction. Since a few days ago I only receive new messages but if I want to send (or reply to) a message, a note appears saying "your message cannot be sent due to system incompatibility - Error N. 007."
What can I do to restore full work capacity to my gmail.com ?
Thanks,
please reply to my e-mail address sjradzik@gmail.com