Does the message show right after you click on Sleep, or when you wake the computer from Sleep?
It looks like the file PTUMLMBMP.SYS is associated with the USB Mobile Broadband Device Driver.
Do you use a USB broadband modem (stick) to connect to the Internet?
In that case, I suggest re-installing the USB broadband Verizon program and the drivers.
First, uninstall it, restart the computer and re-install it.Let me know if the message will still be there.