If you upgraded VisualSVN Server like I have today to 1.61 and have Trac installed as per VisualSvn+Trac then you’ll notice Trac stopped working.
To fix this, follow this part of the instructions:
Add following line at the top of file C:\Program Files\VisualSVN Server\httpd-wrapper.bat:
set PYTHONHOME=%~dp0\Trac\python
Update: Later updates to VisualSvn Server break Trac.