Validation battle: Win vs. Linux

I have a courious workunit:

http://einsteinathome.org/workunit/2020186

That WU was crunched two times with Windows and two times with Linux.
Both Windows results have the same checksums, they counted as valid. Both were done on Pentium 4 processors.

http://einsteinathome.org/task/8517806
http://einsteinathome.org/task/8517807

Fstats.Ha: bytecount 1806116 checksum 86568931
Fstats.Hb: bytecount 1539225 checksum 73774351

Fstats.Ha: bytecount 1806116 checksum 86568931
Fstats.Hb: bytecount 1539225 checksum 73774351

Both Linux workunits have the same checksums, but they are diffent to the Windows one and they are counted as invalid! Both were done on Athlon 64 processors.

http://einsteinathome.org/task/8517808
http://einsteinathome.org/task/8517809

Fstats.Ha: bytecount 1806116 checksum 86746406
Fstats.Hb: bytecount 1539225 checksum 73930394

Fstats.Ha: bytecount 1806116 checksum 86746406
Fstats.Hb: bytecount 1539225 checksum 73930394