I too have had the same problem. The 1st Feb security update seems to have disabled Rosette which has been the translator for PowerPC applications to work with SnowLeopard. Appleworks and old word for Mac have been affected oin the ways described below - i.e, files open but crash the application when saving is attempted. Otehr applications may also be affected if they depended on Rosetta.
I have had exellent support from AppleCare and spent most of the day trying various remedies. Ultimately the only easy solution seems to be to reinstall everyting on your hard disk prior to 1st Feb when you installed the update.
Take a deep breath - insert your snowleopard disk 10.6.8 (check that it is grey - if its not I don't know what to do!) Shut down and restart holding down ALT key then open the disk image and then go to the top menu on the screen (not in the box) and follow instructions from there. It normally takes about two hours, Everything after 31st Jan or when you last updated Time Machine will be lost but everything before that date should be safe.
You will get a message saying that there is aoftware witing to be downloaded - DO NOT DOWNLOAD IT - the offered update will be that of the 1st Feb that caused all the grief.
My adviser t Apple told me that it is important to file a bug report with Apple about this. Unless enough people report this to Apple the next security updates will not have been corrected and we shall have to go through all this agony again. I have no idea if and when it will be safe to dwonlod all or part of later security updates. This the option of disabling elements of the update, but my advisor could not give me any ehlp about that. Lets try to keep in touch here and try to make sure that everyone who falls into this trap tells Apple about it to prevent repetition.
i hope this is helpful. f anhyone affected is still on AppleCare please contact them and report the problem. There may be a better way round this but my AppleCare Level 2 expert could not help any further today.