well, I don’t understand it What I’d do but don’t have time for just now are traces. If you can, add extensive traces to PreviewPane.s file. Every function enter/leave should be traced and also interesting branches of code. It should reveal code flow and maybe reasons why it behaves this way. I especially don’t understand partial load after code change.
If you haven’t used traces before, examine tdbg.sh file where are my comments and then I’d recommend to read article Reid wrote about TDBG: [url:38asrboy]http://www.multieditsoftware.com/TheDev/trace_facility.htm[/url:38asrboy]. Or maybe in opposite order.