I had a similar problem with model pack 12,try this:
First paint your segements,load up map,they would proberly be invisible like you said.
Then,select paint wall ONLY,delete the wall segements,then repaint them using the same method as you deleted them.
Load up map again,they might show up this time.
This may not work as this is a solution i came up with for model pack 12,also it could be a version of fpsc you are using thats causing the problem?
Also try using the fpsc cleaner between saves,it may help.
Your signature has been erased by a mod please reduce it to 600x120 and no anim.
