I don’t know what did cause your error but for sure Panda 1.6 does support RGBA.
There is a topic in the manual discussing few problems with alpha channel… It might be linked to that.
En espérant que cela t’aide
Although panda supports RGBA in certain image formats like tiff and png, it doesn’t support RGBA BMP files. In fact, I’ve never heard of RGBA BMP files before; it must be a relatively new addition to the format.