XEmacs can't delete big chunks

If I load a big file (>50000 lines) into XEmacs v21.5beta17 and delete a
big chunk with, like, C-u 20000 C-k, XEmacs just sucks CPU until I kill
it.  My solution: use vi for just this case.  I've had this problem for
many months (years?) on different machines and versions of XEmacs.  Am I
the only one?

-- Pete