I still can't reproduce the problem.
Does this happen in a default configuration? Start SlickEdit with a temporary configuration directory "vs +new -sc c:\temp\testvs\", then open your project and enable symbol coloring and see if it happens.
Another way to go about this is to edit the following file under your SlickEdit macros directory: se/color/SymbolColorAnalyzer.e, after line 260, add the following statement: _StackDump(); You may need to run SlickEdit as administrator to give yourself permission to modify this file. Then, from the slickedit command line, type "load" to compile and load the module.
This will produce a bunch of debug output to a separate window. Click in that window and hit Ctrl+C to cut/copy the text, and then post it here. That should expose whatever is triggering symbol coloring to reset and redraw frequently.
Remember to remove the debugging code after you are done.