Call it a wild guess but I'm gonna go out on a limb and say .... muslims did this.
possible - it is common knowledge in Burma that there are government people getting investments from Saudi donors who are building mosques, etc.
Government terror is more likely though. The EU is all over Rangoon, the government doesn't want people saying anything negative about the country to foreigners. Right now video (mostly pirated), gem, and other businesses are being shut down completely while foreign investors are in town.
In this case and in others in the past, rumors about an impending attack run wild through the targeted neighborhoods several weeks before they occur.