To reproduce: 1) Open Visual Studio 2008 with R# 3.1 installed 2) Open any solution (I used default console application project) 3) Open any two files (e.g. Program.cs and AssemblyInfo.cs), switch between them (mouse or keyboard) - snappy 4) Menu "Tools -> Options...", choose "Fonts and Colors" section and close the dialog with "OK" button (no changes) 5) Try switching between the files (mouse or keyboard) -> significantly slower (takes about 1 second on my machine to switch) To ensure this behaviour was triggered by R# plugin, I loaded Visual Studio 2008 without R# (holding SHIT during Visual Studio shortcut activation). Repeated steps 1-5, no slowdown was noticeable.