Ok, the diagram helps a lot.
A couple more questions:
Why are you using firewall at all ? You don't appear to need it.
I presume that g7szb has an appropriately configured IPIP tunnel
back to 192.168.2.* via g7tgr ?
So, to summarise the problem again:
g7tgr is a linux based router running 2.0.29 revision kernel with
AX.25 and IPIP encap support. It has an IPIP tunnel to g7szb via
an AX.25 lan. When you attempt to ftp files between g7tgr and
any of the MS Windows for Workgroups hosts on the ethernet network
supported by g7szb, you get kernel panics on g7tgr ?
Have you confirmed that you do _not_ get kernel panics when you
ftp to/from g7szb itself ? Is there any difference between ftping
to the 44.* address of g7szb and ftping to the non-44.* address of
g7szb ?
The answers to these questions will help narrow the problem down a
bit.
regards
Terry