Why do you need extensions so bad. You can basically do most of the stuff in the bonus packs with out the bonus packs. Try to get better at coding without them first, then try some extensions, you will learn much more and become a better coder than you would starting out with extensions.
"Computers in the future may perhaps only weigh 1.5 tons."
-Popular Mechanics, forecasting the development of computer technology, 1949
Takes skill to use the extensions right too, in most cases, they just give you more control over what you're doing.
For instance, the Platform Object. It is NOT easy! I managed to create my best platform engine yet with that thing, but it took a lot of work, in some cases even more than a static platform engine would, but once you have it sorted, it's so much more accessible.
There's nothing wrong with extensions. Those who can't work out how to do what the extensions do without using it will have trouble with the extensions themselves anyway, because they usually do take some initial knowledge.
After installing MMF you of course applied the latest update (build 117) before trying out the bonus pack. I may be mistaken but as far I as remember the bonus packs require the latest version of MMF to work.