File is different when read from NFS server
Solution 1:
Ok so it turns out this is a bug with the bxe driver in FreeBSD 10.0-Release specifically
The bxe(4) driver can cause packet corruption when TSO (TCP Segmentation Offload) feature is enabled. This feature is enabled by default and can be disabled by using a -tso parameter of ifconfig(8). It can be specified in rc.conf(5) like the following:
ifconfig_bxe0="DHCP -tso"
This bug has been fixed on FreeBSD 10.0-STABLE.
Many thanks to junovitch on the FreeBSD forums for figuring this out.