Gmail won't send emails from my Mac!

[mtgm]

When I use my sister's computer (PC) everything's fine; but attempting to write or even reply an email is just impossible! I have a MacBook with a Mac OS X version 10.4.11
(Also, when I spend more than 2 minutes on YouTube my Safari just shuts down completely, can this be somewhat related?)
Any insight would help. Thanks ahead!

 

[iBookG4user]

Are you trying to send email via Apple Mail or in Safari? Also, do you have all of the latest updates?