Mine was doing the same thing. Did you wipe data/cache before install? Did you restore any apps from TiBu or MUIU backup?
What I finally did to fix mine was to wipe data/cache. Then I performed a clean install. After reboot, I skipped the sign in and set up my wifi. Next I signed in to the market and downloaded all my apps. After that I restored some app data from TiBu and restored some settings from MIUI backup. Mine is working great again. dancedroid
I performed a wipe data/cache when I first installed MIUI originally version 1.2.19.0 but when I didn't have any google apps at all, phone wasn't synced up to google so I performed a restore to a prior MIUI backup I had to a prior version and than did a straight upgrade to 1.2.11.0 w/o doing a wipe data/cache..
How can I make sure if I do another wipe data/cache I won't lose my google apps to allow me to get access to the market and such and re-download my apps?