I hope when you say that you upgraded from 4 directly to 6 that you don't mean you installed LabVIEW 6 over 4. NI gives you the full installation disk for 6, and all sorts of aughful things can happen if you try to install it over a previous version rather than into a different directory. If your only problem is that when you mass compile certain VI it doesn't find certain subVI's, you might try adding the directory into the VI Search Path in the Options. If this does not work, you might want to try seeking out the problem subVI's and open them. Sometimes VI's become corrupted and will not be recognized as a valid VI. If they open OK, I wouldn't worry about it too much. When you go to use those VI's you can direct it to the correct subVI and then save the cha
nges.