I have solved the problem, i will post a solution to the issue that was causing my problems incase anyone else suffers the same problem:
A likely cause is the file that stores cookies may be corrupt. To test this close Firefox, go to your profile folder and rename cookies.sqlite to cookies.tmp
Restart Firefox, log into those sites and then see if it remembers the logins.
Other solutions to a problem like that may be:
For other possible causes, first try clearing the cookies for the site, there may be a malformed cookie causing the problem. In the Firefox menus select Tools > Options > Privacy - In the Cookies section click "Show Cookies..." to access the option for removing cookies.
Also make sure that cookies are being accepted and not being deleted when Firefox closes. Go to Tools > Options > Privacy, on that dialog you can make sure that cookies are being accepted, then in the private data section make sure that Firefox is not set to delete cookies when Firefox closes. Also click on the Exceptions button in the cookies section to make sure cookies from those sites are not being blocked.
Next check any internet security software to make sure it is not blocking or deleting cookies. Some internet security software has privacy options that can block or delete cookies.