Not supposed to import/export wdrs like that. Delete shadows scripts, they stopped being used over a year ago, all you need is GIMS + OpenIV.
The correct method for exporting an editable wdr from GTAIV is to export the chosen wdr into an odr and .mesh file then import the odr file with GIMS. (right click the file in OpenIV to see the export open formats option)
After using GIMS to import the exported .odr, now the model is in 3dsmax ready to edit.
To export the file you need to export an odr using GIMS, once that's done use OpenIV to open the chosen .img archive and drag+drop the new .odr into the OpenIV window and OpenIV compiles the .odr+.mesh file into a normal .wdr (only need to drag+drop the .odr, not the .mesh file because that gets found automatically. This post has been edited by Frank.s on Saturday, Jun 9 2012, 13:12