Armory upgrades doesn't work right

The Armory in StarCraft 2 Campaign doesn't seem to work right. Here's the story,

I played up to mission 22, most of them on brutal - without ever upgrading via Armory or Researching abilities. There is a few missions that I was not able to beat on brutal because of the no upgrades, so finally decided to use my 1.7million credits to upgrade. Now here's the gay part, all the upgrades does NOT work on any of the 22 missions that I have played, same goes with the researches. The upgrades and research will work on the missions after though. There is something else that I noticed. In this mission, http://www.youtube.com/watch?v=X2P7kOOpTug - he was able to build diamondback and marauders, while I could not.

Can someone please tell me what is wrong with my campaign?? Any help is greatly appreciated.

--edit--
I just realized I posted in the wrong forum, will a mod kindly move the topic to the appropriate forum?

 

Research can not be used on previous missions, hence why you should upgrade from the armory asap rather than wait til the end.

As for the diamondback, he did the missions in a different order, so he got the diamondbacks from the Train Robbery mission before doing the Terrasine Gas mission.

You must be really good to go brutal without using upgrades, I'm having trouble doing hard even with upgrades.

 

When you complete a mission, it permanently saves what upgrades and units you had unlocked for that mission, so when you go back to replay it (from the mission archives) you can only use those units and upgrades.

But that's really not a big deal, most missions you can handily beat just by massing the new unit that is given to you for that mission. (Even in "Welcome to the Jungle" on hard, I just massed only goliaths and was able to beat it, get every research piece, lose no SCV's, and prevent them from sealing any altars)