The English version of the message is "locking existing frames", and it indicates that After Effects is determining which frames are already cached into RAM before it begins the process of rendering new frames for RAM preview.
Make sure that you've installed the latest updates. They fix a lot of problems, including one that caused the "locking existing frames" phase to take too long in some cases.
If that doesn't help, then we need to know a lot more if we're going to help you. Please provide answers to the questions listed here: "FAQ: What information should I provide when asking a question on this forum?"
Actually I only ever have seen that message with multiprocessing, so maybe turn that off, if you are using it...
Sorry, I totally missed to add more information. So here it is:
I'm using AE CS5 Version 10.0.2.4,
Windows 7 64-bit Professional,
I'm cutting the AVCHD clips from the camcorder (H.264 in mp4),
my laptop has an Intel Core2Duo T8300 with 2,4 GHz,
4 GB RAM,
NVIDIA GeForce 9300M GS,
no external hard drives.
But now here's a big difference:
I'm now using a (same Windows) desktop PC with an Intel i7 2600 Quad with 3,4 GHz (and Hyperthreading, so 8 virtual cores),
I now have 16 GB RAM (4 GB are used as RAM-Disc, so cannot be used by programs),
it uses a ATI Radeon HD 4600 graphics card.
Also no external hard drives.
On my desktop PC I now use the rendering of multiple frames. The locking occures there, too. What suprises me, is that it does that for a RAM preview, but the area it is supposed to render doesn't have any prerendered frames and is only 3 - 4 seconds long. So it defenitly tries to check every frame which is stupid.
I just tried to empty the hole image cache. It still locks frames.
It also disabled multiprocessing because of some effect or expression. So that doesn't seem to make a difference...
I would highly appreciate if you also could quickly answer another question:
What codec would you recommend instead of the slow H.264? I've tried some but none really worked. So tips are welcome!