We got these msgs sometime, too.
Seems that the ACD wants to send RPN to aspect via modem and got an error.
Perhaps Aspect has diasabled the dialin-account on their RPN-server, too.
Check modem connection, phoneline, rs232 cabling.
Sometimes the NT RAS-service freezes, but that should be corrected by the reboot.
Look in logfiles, why the ACD wants to send RPN. Btw: if you reboot the ACD, it tries to inform Aspect about that via RPN, too...