No need to reconvert the map back to gif.  The standard image format Poser usages is jpg although PNG is a better, lossless standard.  Still, if you can provide a screencap of the MatRoom with all connecting nodes open, we might see something we are overlooking.  If the UVMapping and texture map matches in the 3rd party application, the only place where mismatching can occur would be a MatRoom setting on a node.