By any chance, do you happen to have 256k SIMMs *and* 4M SIMMs
installed on your SE/30?  If you do, I suggest that you make sure that
4M SIMMs are installed in Bank A and 256k SIMMs are installed in Bank
B.

Apple's _Guide to the Macintosh Family Hardware_, 2nd Ed. says the
SIMMs installed in Bank A must be larger or equal in size to the ones
installed in Bank B.  From my own experience, it doesn't really seem
to matter when you have 4M and 1M SIMMs, but it apparently matters
when you have 4M and 256k SIMMs (I helped someone with SE/30 by having
him correct the order of the SIMMs).

The four SIMM slots closer to the logic board's front edge are Bank B
slots, and the rest four slots are Bank A.

If it doesn't help, please repost here with your system's
configuration as detailed as possible.

Thanks,

ken