German,
I've experienced the same issue, but the methods here:
http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/100/p/177902/783547.aspx#685829
appear to have worked for me. I'm using a 2.6.37 kernel, though, and had to modify the code to use the iomapped memory rather than using the davinci_* macros. Additionally, I am only using one-shot mode and not continuous.
I don't really understand how the hardware gets into this state, but I believe that the problem lies in hardware and not software. There are a few messages on this forum in which people experienced the same issue when using the hardware directly and not through any kernel drivers.
Best of luck!
-M