I had similar problems until I moved all the necessary files (ISDbg.exe, SciLexer.dll, Setup.exe, rul-files, etc.) to a directory directly under the root of the target machine (C:/debug). Then I created a batch file called RunDebug.cmd inside this new directory with the following two lines: ISDbg.exe /regserver Setup.exe /d"C:\debug" Then I ran the batch file and the InstallShield Script Debugger opened as expected. This was the only way I could get it running. I hope this helps.
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