JRE 6u2 breaks 6u1 files

I have a program that uses an ObjectOutputStream to write some files,

I was previously using 6u1, when I updated to 6u2 my program fails to load the files outputted by 6u1.

Any newly created files using 6u2 work fine though, it just cannot read 6u1 created files. I am afraid if I just start over it might happen again with 6u3 or java7?

Can someone shed some light on how to resolve this. I am currently considering disabling automatic updates to allow the older files to keep working.

[511 byte] By [VCreatora] at [2007-11-27 11:27:48]