you have nvidia video card working in your mediator? wow!
so you can browse with indivision, while you cant with the rtg. the rtg card in this case your nvidia provides buffer memory for pci dma, on which the network card usually relies. you should make sure this shared memory is at least 1 mb i guess. the settings for that as well as fast ram might be tooltypes in your monitor file. i dont remember and im away from my amiga to check.
ah and changing endiannes of display may (but not must) lead to a crashes since the dma buffer gets corrupted/overwritten. you may try to use the oposit endian mode, the tooltype to enable more mdes is something like showmode=essential>all. ah, perhaps these are not tooltypes but env varibles.