Strange icon in RTC

I believe the red square indicates that the image decorator that represents the state of the file could not be loaded from disk for some reason. The usual reason is that it is missing from the install but it could also be that the image file is corrupt. In order to determine what the cause is, it would be helpful to know if the image was always present on that file or did you take some action that caused it to appear? If so, what was the action? If not, is anyone else on your team is seeing the same thing on the same file? If they are not, are they using the same version of the RTC client?

Another possibility:  The JDT uses a red square overlay on the bottom right of an icon to indicate something is "private class" (see http://help.eclipse.org/helios/index.jsp?topic=/org.eclipse.jdt.doc.user/reference/ref-icons.htm ).  If that overlay action is activated, it might be overriding the yellow cylinder overlay indicating it is under source control.