Okay, I think I found the problem:
I had a look at the GPU clocks in Catalyst Control Center, and it seems that the 3D clock won't start by default when playing a 3D application in windowed mode.
The graphics card stays in its 2D powersaving mode, which might be the reason why the game freezes or crashes after a while.
Guess it's time to go back to fullscreen gameplay.

Alright, I'm finally desperate enough to ask for help.
I've searched for the following here on MATY, MTS2 and Google in general: right-click, right click, M&G, K&B, IKEA, graphics, driver, crash, freeze, Nvidia, ATI, Radeon. Apparently I'm alone with my problem.

It wasn't until April that I installed the IKEA, K&B and M&G SPs -all in one session- to complete game. When I did this, I made sure to follow the installation advice given here, so a faulty installation should hopefully not be the problem.

My system specs:
AMD Athlon 64 X2 Dual Core Processor 4800+, 4 GB RAM, ATI Radeon X1950 Pro, OS: still WinXP
The driver is freshly updated for TS3.

The problem:
Since I prefer to play in windowed mode, I'm used to moving the camera by right-clicking on a spot or holding the right mousebutton down while dragging the cursor across a lot, and that never caused any trouble when I had all EPs and SPs minus the ones above.
Now it's completely different: About 3 out of 10 right-clicks result in freezing or game crashes, and sometimes, but only if I'm lucky, VPU Recover will reset my driver.

What I've tried so far:
-changing the in-game settings to every possible configuration: shadows, details, smooth edges
-changing the Radeon CP settings to every possible configuration
-eliminating the usual suspects, i. e. cutting/pasting the mydocuments\EA Games\The Sims 2 folder to my desktop and letting the game generate a new one (I'm not sure if this was really necessary, but I did it just in case.)
The game installation itself is untouched (no lighting mods and the like), except for cleaned 'hood templates.
-reinstallation of the graphics driver
-starting the game with the onboard graphics (Nvidia 7050M-M) and the newest driver, same drill as above
The Nvidia CP has no driver reset function, so the game simply froze, then crashed.
Fun fact: For sheer fun I briefly replaced my shiny Radeon card with my old Geforce 5200 FX and was utterly amazed that despite the shitty graphics and jagged edges, I could right-click to my heart's contents without any trouble at all. WTF?

Right now, I am at the end of my (limited) wisdom. The only thing I've avoided so far is a complete reinstallation of the game and all EPs/SPs, and I really hope that it's not necessary.
I'd be really glad if some awesome person was able to point me the way to a solution.

I agree, it's really frustrating.
Exactly the same thing happened to me when I moved one of the sons and his pregnant wife (yes, he IS the father) out of my active household.
At first I suspected that it happened because I switched to "edit town" mode immediately after kicking them out, but in your case it happened even without doing this (I hope I got that right).
Seems that moving an expecting couple somewhere else resets the fatherhood to...well, whoever, which is a major nuisance.
Not only does the child lack the ties in the family tree, but the "have a grandchild" want of the husband's parents is not fulfilled, and if this wasn't bad enough, I cannot even be sure if the actual father's genetics have been passed on.
Only time will tell. *sigh*

*Edit: I'm using Awesomemod as well, parthogenesis enabled.

Strangely enough, even infants and toddlers get the "nice stuff" moodlet from the reward fridge.
In addition to that, it seems to hold an endless amount of food forever, i. e. without getting spoilt, so if you chain a retired celebrity chef to the cooker for the end of her/his life, you can provide high-quality meals for at least the two next generations.
There's a smaller reward - a food processor - for the culinary career as well, but it might just be the one from the buy menu.

AFAIK, the top of the medical career brings you tons of money but no reward item.

*edited due to stupidity