My Amiga doesn't like exec.library 45.20 (OS3.9).

[matthey]

There are other newer programs that add memory at a physical address to the free memory pool. They might work. The ROMTAGMEM maybe adds a reset proof program to add the memory at bootup. The old ROMTAGMEM reset proof stuff maybe interferes with the newer AmigaOS 3.9 reset proof update.
The Kickflash I believe plays with the ColdCapture, CoolCapture, WarmCapture reset proof workings as well.
Someone else can probably recommend a good program to add memory to the free pool. The first 2 arguments for ROMTAGMEM are probably the location and size of the memory to add?

[matthey]

The first 2 numbers are probably the physical addresses of the memory to add and the second 2 maybe the memory priorities of them? We need Piru for this one. He has all the answers on these hardware specific problems ;-).