If I understand you correctly, a video CD produced on your PC won't run on MIL's DVD player, but one produced by SIL will. Is that right?
There are two possibilities, I believe: One is that MIL's DVD player is fussy about what brand or type of CD you use, or even what machine has been used to burn it. CD-RW are more likely to be unreadable than CD-R in a domestic player, and unbranded disks could be a problem too.
The other is, how your software compiles the slideshow. What software have you and SIL used to create your VCDs?