This is for µVision 3, Version 3.12a, independent of the microcontroller type.
Since some time the Memory view in the debugger uses a super small size with its font, each character is just one pixel high. The dialog "Configuration", tab "Colors & Fonts" tells me a font size of 12582911 (0xBFFFFF), but it can't be changed. The other views are reported as using a font size of 0 (zero) and are readable.
I'm not able to tell when or how this crept in since I don't use the debugger very much, and the Memory view even less. Which registry entry or which configuration entry in which file should I correct to get the standard size back? Or is the executable damaged?