Here I am again!
As I suspected, the error wasn't solved. Only has changed the place where it occurs.
As you said, I've checked the timing requirements, and I have found that they can't be modified. We are using the 71V416 ram chips, which are the ones used by the SOPC. I've read that the class of this ram assigns the timing requirements automatically, so I can't see any way to improve that...
Also I've done a small RAM test, writing values and checking them, and it doesn't seem to fail...
I'm completely lost :-(
aLeX