Kernel 2.4->2.6 upgrade results in PANIC: could not locate a valid checkpoint record

Hi, we have happily been running postgresql 7.4.x (currently 7.4.12) on a
debian linux with kernel 2.4.x for some years without any issues.
Yesterday after switching to 2.6.16 we experienced the following problem
upon pgsql startup:

LOG:  could not open file "/var/lib/pgsql/data/pg_xlog/0000006900000091"
(log file 1 05, segment 145): No such file or directory
LOG:  invalid primary checkpoint record
LOG:  could not open file "/var/lib/pgsql/data/pg_xlog/0000006900000091"
(log file 1 05, segment 145): No such file or directory
LOG:  invalid secondary checkpoint record
PANIC:  could not locate a valid checkpoint record
LOG:  startup process (PID 414) was terminated by signal 6
LOG:  aborting startup due to startup process failure

After reverting back to kernel 2.4, postgresql started up hapilly again.

Any ideas?
--
-Achilleus