Tested with:

--- Windows 8 x64 Pro with Media Center, NVIDIA GeForce GTX 570 ---

In versions:
--- 2.68.5 r60294, and 2.61.0 r42615 (couldn't find a version without the problem) ---


Blender stops responding for some seconds when moving to another frame after CTRL + Z (or right after opening the .blend file)
What I notice is, when I click in the strips view to navigate through the frames, something is loaded into RAM (in my project, aprox. 3 GB of RAM is taken), and then the processor does something, while Blender remains stuck.
I'm working in a not-so-complex project, where the final video is bigger than 1 one hour (30 fps), but with just 15 minutes of stripping (most of them are audio files, then there's a constant video, and small effects),
it takes more than 10 seconds each time Blender is opened, or when I try to move after a CTRL + Z.


To reproduce:


-Extract and open the attached .blend file.
-Create the folder structure for the attached file "dummy.mp3".

That is, the following path must exist:

F:\ALB3530\Music\SOUNDS\Soccer\Dummy.mp3

This is the audio file that is repeated over and over the sequencer.

-Open Blender, load the attached .blend file, and click anywhere in the strips view, in order to go to any other frame.

You'll notice there will be a delay, where Blender stops responding, and recovers after some seconds.

In the following machine:

Windows 8 x64 Pro
Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz
16.0 GB RAM
NVIDIA GeForce GTX 570


It takes 5 seconds for Blender to respond, considering that's a very simple project.
With a bigger file and a complex project, it could take more than 20 seconds.

If you duplicate some strips, to simulate a more complex project, it will take more time for Blender to recover.