Using an almost new SanDisk Ultra USB 3.0 32GB, working back and forth between several computers with files I was moving around, I began getting the message “already running” upon clicking the application RunSanDiskSecureAccess_Win. I tried some of the above suggestions, which did not work as described but gave me an idea that did. I opened the folder SecureDiskAccess Settings, looked for the most recently created .dat file, noticed it contained the word “lock” in it, and deleted that file. Problem solved - apparently. Am now again using this thumb drive as intended.
How did I create this problem to begin with? Probably by mindlessly yanking the thumb drive out without logging out and/or dismounting it from computer A, then attempting to use it again in computer B.
Time will tell if there is more to this problem than it now seems. If the problem recurs, I will follow up on this post.