If you uninstall your game, you might want to try this: http://download.cnet.com/Revo-Uninstaller/3000-2096_4-10687648.html  It digs all the way down the registry and gets rid of all traces of the game.  I haven't had any issues with Revo, and the reviews of it are good.  And it's free. 

Good and free.  If it came with vodka, it would be perfect.

I like redundant threads.  It saves me the trouble of scrolling all the way down the topic list.
 
Anyway, here's something that could help. http://www.modthesims.info/showthread.php?t=381540 The blue lot fixer seems to help, but it's tedious to use if you have a lot of cc.

No luck.  I installed new drivers but still having the lag problem.

I've had Blue Lot Syndrome several times.  It seems some of the cc doesn't agree with the game.  Try this: http://www.modthesims.info/showthread.php?t=381540

I installed and ran all my cc through the fixer and haven't had a blue lot since.

Mea culpa -- I get so excited about new drivers I forget how to spell.

NVidea = NVIDIA

I've got the RealTec problem, too.  I went to PC Pitstop and ran their free driver update finder.  RealTec has a new driver for the card, and I'm downloading it now.  Also, NVidea had a new driver available.

PC Pitstop -- http://www.pcpitstop.com/pcpitstop/

RealTec -- http://www.realtek.com.tw/downloads/downloadsCheck.aspx?Langid=1&PNid=14&PFid=24&Level=4&Conn=3&DownTypeID=3&GetDown=false

NVidea -- http://www.nvidia.com/content/DriverDownload-March2009/confirmation.php?url=/Windows/195.62/195.62_desktop_winxp_32bit_english_whql.exe&lang=us&type=GeForce

I'm having similar issues -- I communicated with the spirit in the hidden garden once and got his remains, which were to be put in the tomb next to his wife's remains.  I was able to get to the tomb, but couldn't get rid of the remains.  The game went all BlueLot on me after the save, and when I reopened an earlier save with no cc and tried to redo the mission, the spirit wouldn't communicate with my sim. 

The remains are no longer in my sim's backpack, the people who own the Hidden Garden house keep calling and requesting my sim to come and talk to the spirit, but when my sim gets to the house, the dialogue box is blank when the house owner greets my sim.  When my sim mourns (which should call the spirit), nothing happens.

I had a mess of cc on my lots, and kept having to revert to older saves without cc.  I recently (today) got this Blue Lot fixer (http://www.modthesims.info/showthread.php?t=381540) at MTS and am going to run my cc through it.  If I find it makes a difference in completing missions, I'll report back. 

I got the Flagrant System Error pop-up indicating that a "boss" was invalid.  I had a playable ghost who got a job at the Science Lab and leveled up until she was in charge.  She eventually died permanently ("X has lost her grip on the mortal coil.  X will come back to visit, but cannot be rejuvenated.")  Three other members of the household "worked" under her, and the Flagrant System Error would show up pretty regularly.  It didn't seem to be causing any freezes or other problems, so I ignored it.

That was two days ago.  Yesterday the neighborhood loaded and played just fine, today the neighborhood is gone.  Just gone.  It is an ex-neighborhood.  Its picture is gone, its description is gone, only its title remains.  When I click on the title, it doesn't load.  Other neighborhoods load and play just fine.

Not sure what the heck happened. 

I was playing a legacy and was on the third generation.  The playable ghost was the legacy founder, and her two daughters and son-in-law (heir's husband) all worked at the Science Lab and all had her as a boss.  The non-heir moved out, the heir aged up, the next generation's heir became a Young Adult, all without a crash. The game seemed to save properly.  Then it just left town.

It's a mystery to me.