NetBSD 5.0 and SPARCstation 5 not a lucky combination

[Bill Roman <netbsd%songdog.eskimo.com@localhost>]

I had NetBSD 4.0 running on my SS5 with no trouble, but I couldn't
resist trying a shiny new version.  5.0 installed and boots without
trouble, but it locks up shortly after I log in.

The lockups seem to have to do with console output that includes long
lines (not necessarily exceeding the number of columns) and an embedded
newline.  Usually the long line after the newline is truncated (but its
terminating newline still scrolls), I get a shell prompt, and that's it.
No panic, no messages of any sort, no response to anything but Stop-A.

The machine is a pretty standard 170 MHz model, with a CG6 console.

Anyone have any suggestions on how to troubleshoot this?