Culpeper,
Classloader trojans represent only the class of trojans not any specific kind.
Avast Script Blocker in the pro version should do a good job of protecting your system.
Users of Avast Home should install a blocker such as Script Sentry or Script Defender. Both are equally effective.
As for the $40 fee for Pro. This is a program "upgrade" fee for 1 year for 1 license. Yes, I know that sounds funny since the Home version has free upgrades, but because the Pro is directed towards commercial users, and is "feature" rich, the fee is appropriate.
Hope this answers your questions
techie