Operating system and graphics card
Windows 7 64 Bit
Broken: (example: 2.69.7 4b206af, see splash screen)
Short description of error
Every time you close the User Preferences you will get a !event has invalid window warning
Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps
Open Blender. Open User Preferences. Close User Preferences. Open Console. You will find a !event has invalid window warning there.