I have seen this very strange problem with Synopsys VCS time to time.

It is actually not related to if you are using the 32 Bits or 64 Bits version and on which type of system you are running the tool.

For both of the pure 32 bits and pure 64 bits runs I have seen this problem occurs.

Synopsys indicates that this problem might happen when you have several installations of the VCS on your system however, I have seen this problem on systems that I am pretty sure have just once instance of VCS.

Ineed I don’t know how I have solved the problem but here is a general guideline :

I think the problem stopped to appear when I got rid of running vlogan and vhdlan commands in my Makefile.

In fact when you have a big design, you may first like to run vlogan and vhdlan separately for each of your source codes and then finally run VCS. However the other solution is just to issue one VCS command and include all of the file names and list into this command. When I did this, the problem disappeared! But I don’t know why!