USB SWAP Memory

hi friends,
I have TDT644 via Flash, and a USB as Swap installed. settings & incubus are installed on USB swap. I can see that all folders on the swap disk are correct via FTP.
BUT
incubus is still very jumpy. when i check MEMINFO, i see that none of my 16376 SWAP file is being used. 16376 is FREE.

total used free shared buffers
Mem: 46864 45180 1684 0 2828
Swap: 16376 0 16376
Total: 63240 45180 18060

does this mean my swap is not working correctly? should i be doing anything else to get the memory allocated to the swap file?

thx