SP cheats - what kind of shit is this?

So, I did this mission on Xil, and after I had (barely, because I was tired and thought the mission sucked) completed it on hard, the post-mission-loadingscreen stopped at 50%. I tried to reanimiate it, but ultimately Blizzard's own error handler decided the game didn't respond anymore and shut it down.

Next day, as I resumed the campaign, I was set to the last save in the mission itself. Like I said, I thought it sucked and also I wasn't really keen on stealing Protoss their precious relics, so I quit and continued with some other missions.

Later, I decided, I might as well now do the Xil mission, and so - yeah, I know, kinda stupid - loaded the old savegame, thinking maybe if I did complete it, it would count to my current campaign progression. Needless to say, it didn't (that's what you get for putting "choices" into an RTS campaign, I guess).

After completing the same stupid mission, which I thought to be the most bothersome of the game so far (because it's mostly about handling that stupid laser), now already twice which was more often than any other mission, I said to myself
+ Show Spoiler [what happens after Xil mission] + I'm gonna load my current campaign progress and quickly cheat through the mission, so I can continue on with what follows afterwards.

As I typed in terribleterribledamage, the game said something about achievements now being disabled blabla mission blabla load game. It wasn't there for very long iirc, or I just didn't read it well enough, but alas, I though "alright, I don't get achievements for this mission if I cheat through it, that's just fair enough". I did a couple of missions afterwards w/o getting achievements - but I hadn't earned any, except for one time, but there it seemed like the connection to bnet had been lost.

These were five missions or so, which I did afterwards, without ever quitting the game. Now I did save my progress, exit the game, eat a pizza, turn the game back on and load the progress, and it says, achievements are disabled until I load an (obviously older and not "corrupted") savegame.

Seriously, what kind of shit is this? Because I cheated in one mission, I can't ever earn any achievement again? I mean, as if I couldn't have set the game on easy (which is probebly what I ought'a have done in the first place, but surely it had taken longer for the damn laser than to pierce through that walls) and got those fucking protoss science relics (not the mission object, bot those used for research), which are the only thing with an impact on my later progress anyways, and which I only took because I had legitimately taken them in my earlier legit attempt.

This is so bothersome. I mean, I certainly was one of those people who said achievements were shit and stuff, but if they are there and in front of my damn nose after every mission and I earned them, I want them to be awarded to me, damnit, and cheating in a prior mission should have no impact on that. Hell, I would easily pass on the damn relics for that.