This paper takes a closer look at the user interface issues in our research multi-modal browser architecture. The browser framework, also briefly introduced in this paper, reuses single-modal browser technologies available for VoiceXML, WML, and HTML browsing. User interface actions on a particular browser are captured, converted to events, and distributed to the other browsers participating (possibly on different hosts) in the multi-modal framework. We have defined a synchronization protocol, which distributes such events with the help of the central component called the Virtual Proxy. The choice of the architecture and the synchronization primitives have profound consequences on handling certain interesting UI use cases. We particularly address those specified by the W3C Multi-Modal Requirements, which are related to the design of possible strategies of dealing with simultaneous input, solving input inconsistencies, and defining synchronization points. The proposed approaches are illustrated by examples.