I have an Office 2010/Exchange 2010 environment with a <1000 users scattered throughout many geographically separated sites. They are seeing a delay when crafting email messages (both new and replies) and when browsing between folders. The delay varies between 5 seconds and about a minute. During the delay, if they continue typing, the text will pause on the screen, only to appear after the delay has ended (as if typed very fast). When browsing between folders, the contents of a folder do not populate for the duration of the delay, then suddenly all messages in a folder are visible.
We used cached exchange mode with local profile storage of the OST files for the locally installed users, and remote profile OST files for those using a terminal server. Both local and remote users began reporting the problem at about the same time, with no Exchange changes preceding the beginning of reports. Exchange performance metrics look good and the problem is not global (one user sees the issue while their neighbor does not). Site link speeds (small user count behind T1s, larger user counts have larger pipes) shouldn't be the issue, since it happens for users in terminal server (2008R2 RDS using shared namespace and Connection Broker. No Citrix.) which is in the same gigabit core network as the Exchange servers.
So now is the point where I admit defeat and come to the TechNet community. Can I get any leads that you can think of? Any tools I could put out there to capture client metrics of one of these events? This is one of those cases where I can't reproduce the issue myself, and I only have trouble tickets describing the same behavior sporadically throughout the organization. How would you approach it? It's driving my team crazy trying to track it down...