Problems with areaportals

clicky
That's what it means by two areas. Even if your areaportal is touching the walls, if it is possible to travel from one side of the areaportal to the other without passing through a different areaportal, it leaks. So basically you need to find good places to put more of them in.

First off, make sure you use the Interlopers Compile Error Checker whenever you are unsure of errors. Just copy and paste your compile log and press Check Log.
Here's a tip:
-Compile your map with Normal BSP, No VIS, No RAD (make sure Do not run game after compile IS selected, you don't want TF2 to launch).
-Select the Map menu > Load Pointfile > Yes
-Hold Control and Zoom out all the way (this zooms out evenly in all 2D views
-Look for red lines. These represent leaks.
-Using the 3D view follow them to see where your leaking through brushwork
-Make sure in your Visgroups you have func_details and props turned off because they have no effect on leaks, and it will be easier to see the lines this way

Good luck, let me know if you have any problems!