i found the error off a site
This error basically means that you’re computer has run out of memory.
This could happen at any time during the compile process, but it mainly happens during the vis or lighting stages.
Try restarting you’re computer before you compile the map to free up memory.
Don’t have any programs / applications running in the background, that you don’t need.
Install more physical memory.
Make sure you have at least 1GB of virtual memory (swap files).
Make some of you’re brushes detail.
thats the site
and where did you get radiant 1.5?