I applied ExchSP1 last week to fix an issue with RUS. The RUS issue was resolved but ActiveSync is now broken. All my AS users keep getting the HTTP_500 error. OMA works fine so I know the virt directory is still okay. I have since applied SP2 but with the same results. I have gone through all of my settings and they are (I think) okay. I did use RUS to change some SMTP addresses using the default policy but I did not change anyone’s primary SMTP address. I went back and changed my mailbox back to the way it was when it would actually sync but it did not help.