Thanks again, I was going out of my head trying to fix it! I do have a question relating to it. What on earth do those mask.... settings relate to? I gather they are related to bmp files??Just curious but I am getting lightning frame rates now. However, in an attempt to figure out what was happening to my PC with the memory error messages described above, I have no idea what might be the reason for the improved frame rates because :1. I re-installed my ATI driver2. Flashed the memory and updated the bios (I think it has something to do with this)3. I ran FS manger and clean and relocated old Landclass files4. I ran got rid of a number of duplicate AFCAD filesHope someone can gain benefit from my mistfortune.regardsPaul

The way I vaguely understood it, these settings have to do with the number of landclass layers used to adjoin different landclass types when they're next to each other. The original topic to discover this can be found here:http://portal.fsgenesis.net/index.php?name...ht=maskclassmapIt was included as instructions in part of another patch file for additional scenery and then it was discovered that the patch files weren't necessary but only this change to the terrain.cfg file. The kicker here is, MS attempted to fix this issue by increasing the allowed number of adjoining layers in the FS 9.1 patch. Holger S. and Justin on the FSGenesis forum are very experienced with scenery and terrain and are good source of information.As for framerates increasing, that's not surprising as your machine is not working as hard, trying to "blend" different landclass types together. Therefor, it can use the additional CPU cycles for other FS threads. The only thing I've been told that is noticeable about doing this is the clear-cut path for power-line towers is now gone. I have yet to notice anything other than that.Regards,