Hi there everyone this is more of a solution thread. it seems to be a popular error with very little documentation for the end user. I recently purchased Call of Duty: World at War with some friends and we have been increasingly adding new maps and playing across a variety of different systems but we all use the same mods folder which gets updated automatically as I add new maps to it VIA my NAS server's built in Folder Sync. the other day we had all tried to launch a certain map which created this "Exceeded Limit of 400 fx assets" error that will cause the game to lock in most cases.  upon hours of searching Google i found that this error generally occurs when mapping ( or creating custom maps ) and was unable to find a fix for the end user. That being said i started messing around with some of the appdata and i found that deleting the servercache.dat file which is located at C:\Users\ACCOUNTNAME\AppData\Local\Activision\CoDWaW has completely fixed the error from appearing all together.  This could very well be a isolated case but i figured id contribute my findings and see if this works for anyone else. Best of luck!

The Waw engine has a limit on assets

This error is saying there are more than 400 FX in the mod you picked

Your right it generally affects mapping, but Ive heard of the users getting the error on occasion

Its most likely just that mod, disregard unless it happens across more than one