Changing button image in toolbar causes text to change

I've been assigned a VB6 issue that I can't recreate locally. A handful of clients are reporting that the text on their Toolbar buttons changes randomly. Below is a video one of the clients sent, illustrating the issue:

http://youtu.be/C_7c9Fe5DAA

If you notice the exclamation mark icon, it's changing color as the button text changes. There's a timer in the app which changes the button's image. I suspect this is somehow linked to the issue, but an stymied as to why.

Here's the code behind the timer:

Code:

---

Select Case tblMain.Buttons("UserLog").Image
  Case "UserLogOn"
    tblMain.Buttons("UserLog").Image = "UserLogOff"
  Case "UserLogOff"
    tblMain.Buttons("UserLog").Image = "UserLogOn"
End Select
tmrUserLog.Interval = 1000

---

The timer is named tmrUserLog. It gets enabled when theirs a message for the user.

Like I said, I'm stumped. Why would the text be changing on the buttons, and why for just a few users?
Thanks for any feedback!

Steve.

Apparently I do not have the plugin installed to view the embedded video

The first things that come to mind though would be
Color depth settings of the PC in question
Theme
Video Card/Drivers

If you aren't changing the value of the FUNCTION, then the video driver is probably confused. Change CASE to whatever each time...