>Anybody else got one of these cards? (It probes as qe0 through qe3.)

Yes, I have on in my SS20.

>Mine works all right, but I get a few messages about lost interrupts
>when I configure it, and during an FTP it regularly prints these sorts
>of messages, in various orders:

I get things like: (I love serial consoles via rtty :-)

qe0: eint: qestat=8000000<CLOSS>
qe0: no carrier, link down?
qe0: eint: qestat=8000000<CLOSS>
qe0: no carrier, link down?
stray interrupt ipl 0x7 pc=0xf000775c npc=0xf00436b4 psr=1e9010c1<EF,S,PS>

despite the above everything appears to work.
I've had these things in sun4c's too same result.  I seem to recall they 
pretty unreliable under SunOS too.

--sjg