According to your description, GVP combo works well in another A2K ?
RAM issue could be solved by running GVP Info utility located on GVP Install disk. Program is able to report various HW components, including origin of FAST RAM - you will get HW ID of manufacturer next to board which added memory to an active RAM pool.
Maybe it's too soon for any dare conclusions, but you might have a Zorro RAM address space collision. If you miss that GVP utility, remove that 4Mb expansion and temporary disable A2091 RAM, that should make troubleshooting a bit easier.
