I don't know if it's a XnView error, or error of Windows, but even if it's a Windows error I strongly suggest to provide some fix in XnView (e.g. add an option to reduce 32 bit BMP to 24 bit for display). If I open such file and store it as BMP in IrfanView, a 24 bit BMP is generated, which is displayed correct by XnView (like 10_M_Irfan.bmp in the screen shot).
In the screen shot you see on the left the display of Windows explorer, on right XnView:

XnView 1.98.2, Win7-64Ult SP1