IMac :: Safri Not Recognizing Usernames For Any Sites

I cannot log into any sites such as this forum with it although the username is right. comes up with a red line underneath it and tells me the username is not correct when selecting login. Im getting this on everysite that has site logins simular to this site. The ones with the separate pop up box are fine.

Also i can#t import any downloaded movies off the internet into imovie although i've used my pc to convert them to mp4 iphone.