@ChrisH
Okey dokey... still no go. Had only tried running through RunInUAE later, after my inability to get the program going. But I just made sure RunInUAE was quit and reinstalled with your script. Same problem.
Here's the SnoopDos log of what happens...
SnoopDos logging started on Thursday, 27-May-10 at 15:29:26
 Count Process Name       Action     Target Name                 Options Res.
 ----- ------------       ------     -----------                 ------- ----
 3     ENV                Open       ENVARC:sys/def_picture.info Read    OK  
 4     ENV                Open       ENVARC:sys/def_drawer.info  Read    OK  
 5     ENV                Open       ENVARC:sys/def_ascii.info   Read    OK  
 6     WBL                ChangeDir  Work:TVPaint3.6                         
 7     WBL                Open       TVPaint                     Read    OK  
 8     WBL                ChangeDir  Env:                                    
 9     WBL                Open       ELF.LazyBinding             Read    Fail
 10    WBL                ChangeDir  Work:TVPaint3.6                         
 11    WBL                Open       TVPaint                     Read    OK  
 12    WBL                ChangeDir  System:                                 
 13    TVPaint            Open       
CON://///AUTO/CLOSE         Read    OK  
 14    TVPaint            ChangeDir  Work:TVPaint3.6                         
 15    TVPaint            Open       TVPaint.info                Read    OK  
 16    TVPaint            ToolType   DEVICE                              Fail
 17    TVPaint            ToolType   PORT                                Fail
 18    TVPaint            ToolType   SUMMA                               Fail
 19    TVPaint            ToolType   WACOM                               Fail
 20    TVPaint            ToolType   KURTA                               Fail
 21    TVPaint            ToolType   NOICONS                             Fail
 22    TVPaint            ToolType   FILEDIR                             Fail
 23    TVPaint            ToolType   PROJECTDIR                          Fail
 24    TVPaint            ToolType   CONFIGREXX                          Fail
 25    TVPaint            ToolType   REXXDIR                             Fail
 26    TVPaint            ToolType   FASTSAVE                            Fail
 27    TVPaint            ToolType   GLOBALDIR                           Fail
 28    TVPaint            ToolType   CONFIG                              Fail
 29    TVPaint            ToolType   NOGAUGE                             Fail
 30    TVPaint            ToolType   NOBORDER                            Fail
 31    TVPaint            ToolType   NOERASEALERT                        Fail
 32    TVPaint            ToolType   UNDO                                Fail
 33    TVPaint            ToolType   PageWidth                           Fail
 34    TVPaint            ToolType   PageHeight                          Fail
 35    TVPaint            ToolType   Screen                              Fail
 36    TVPaint            ToolType   ScreenOffsetX                       Fail
 37    TVPaint            ToolType   ScreenOffsetY                       Fail
 38    TVPaint            ToolType   ScreenOffsetType                    Fail
 39    TVPaint            ToolType   Genlock                             Fail
 40    TVPaint            ToolType   Monitor                             Fail
 41    TVPaint            ToolType   CustomBrush                         Fail
 42    TVPaint            ToolType   Image                               Fail
 43    TVPaint            ToolType   Swap                                Fail
 44    TVPaint            ToolType   TVTools                             Fail
 45    TVPaint            ChangeDir  System:                                 
 46    dos_appdir_server  ChangeDir  System:Prefs/Env-Archive/Ap             
 47    dos_appdir_server  ChangeDir  System:                                 
Closed SnoopDos log at 15:30:03