Hello all, running 08/17 version of Splat here.  Today I found my system unable to open any Sonar files, as well as unable to save a newly created file.  When I navigated to the HD containing my Splat files (not my main C drive) to try and open a file in safe mode, I got the message "D:\ is not accessible.  The request could not be performed because of an I/O device error."  I'm running Windows 10 Home Edition Version 1803.  I'm no computer wizard, but I'm able to handle some basic HD diagnostic stuff, if anyone is able to give me some advice on how to possibly remedy this.  Thanks in advance!
 
            Joel

Is drive d: USB or internal?

Replace the hard drive where drive D: is pointing to and restore that drive's data from the most recent backup. 
Sounds like drive D: is borked

If the drive D: is a USB drive, try unplugging and replugging the USB cable   Also, if USB, check that the drive actually has power going to it. 

It's an internal HD. I'm going to run chkdsk /f /r to see if that corrects the issue. I run (not) regular (enough) backups so I won't lose too much work if the drive is hosed. Lesson learned though: Daily backups from now on.

Given that Windows recognizes the drive (recognizes it, says it's ok, registers the space used/free, etc), I'm hoping some freeware disk recovery software can get me back the last few days of work that I hadn't backed up.

Thanks for chiming in!