Why worry about this? Someone with access to your computer's memory can intercept the unencrypted data, sure, but who's going to be able to get at your computer? Assuming your computer isn't virus infected, has proper virus software and firewalls, and isn't networked to any other computer that might itself be vulnerable, your memory should be safe from anyone without hands-on access to your comp - and if they have hands-on access, you're doomed anyway.
The vast majority of security breaches are from human engineering (obtaining the "I lost my password" info, or finding a password someone wrote down, or so on), not actual hacking. Keep your virus software up to date, don't network your bank computer to any other computer with internet access, and don't write down your password or allow anyone access to your bank computer.