I haven't any problems at all with the two.
As a matter of fact I have been using SP2 and Direct X 9c for about three months and if anything my sim flies better now than before.
Sounds too me like a bad download, I have read other places of similar things happening. M$ admits too SP2 causing problems with certain programs (mainly there own) but I have yet to hear many about and directly related to FS9. And the ones I have read were solved with a reinstall of SP2.
SP2 is a huge file and if downloaded via dial-up is almost guaranteed something too go wrong
You could do a system restore (if running XP) but might be easier to reinstall FS9 to see if that fixes things. If FS9 is the only program giving you trouble then I would try the later.
I'm not one too back up M$ with anything (past posts prove that

) but my experiance with the new package has been 100% improvement in how my computer runs overall.
Also Congo has a post in the software section I belive that has a link to were you can download SP2 and save it to disc, this is how I installed it is from a disc, not M$ auto update, it is M$ auto updating that always (9 out 10) screws my computer up!
p.s. welcome to TheV!!