Sounds like that would relate to MIDI data. Is ksthunk.sys, which I think handles kernel streaming. (You can see this in Device Manager, Properties/Driver tab, then Driver Details. Yamaha tells me that their USB-MIDI driver is installing fine on my machine, except that it’s missing a windows driver at the bottom of the driver stack. And I cannot sync to the keyboard due to the above error message. In my case though, everything shows up in Windows, but MIDI doesn’t actually They assure me that those work for other users of Win7 64-bit. And the latest versions of all their editing software for Win7 64-bit. I am using the Yamaha USB-MIDI driver versionģ.1.2 for Windows 7 64-bit (the latest driver). I have a Yamaha SX70 XS keyboard, which is recognized by Windows as a connected USB device. I have been working directly with Yamaha tech support on the issue for some time. At first, MIDI was working and I could sync up, but after about a week, right around the time I uninstalled and re-installed a MS Lifecam, it failed and has not worked since.

“The following MIDI ports can not be opened at this time”. The error message in the Yamaha software reads The problem is that even though my devices are recognized in Control Panel/ Sound and in Device Manager, no MIDI data actually flows and I cannot sync my keyboard to the Yamaha software that edits it.

Yamaha usb midi driver error 25001