Not a long time ago I started working on a TF2 map again after I've not been doing any mapping for about a half a year. But now that I tried to compile my map, I encountered the following problem that I've never encountered on earlier compiles I made a while ago: A few moments after launching the compile process, the program either loops or completely freezes. Additionally the whole system is acting extremely slow, even the mouse icon is moving hardly and very laggy, so I'm having a hard time just opening the task manager and terminating the process, most of the time I had to restart my computer. At first I thought it was just some simple optimization mistake I made but now that I've looked more into the problem it appears that it's the VVIS process that is having these problems on most of the maps. While VVIS is running, my CPU usage goes up to 100% and it seems to take just too much time to compile than it actually should (I've never actually finished any compiles so I can't really tell if it really would compile or not. But what I know for sure is I had a FAR more complex map compiled in less time half a year ago than I left my alpha-staged map compiling without any apparent progress). The only way I made the map I'm currently working on compile, is removing the big skybox and outdoor areas I drew around the main building and sealing it, because I don't seem to have this problem at all on all-inside maps without skies, that make the system lag aswell but atleast compile in a reasonable amount of time. What has changed to make the vvis.exe process act like this and how could I possibly circumvent the problem of that extremely slow compiling and unusable system? Has anyone else ever experienced this problem before? Here my system specs: Intel Core 2 Quad Q8200 @ 2.33 GHz 4 GB DDR2 RAM NVIDIA GeForce 250 GTS Any help would be greatly appreciated!