I disabled dir_index on the ext3 drive, run ext2fsx and created a directory on the newly mounted drive. I tried to rename the directory which resulted in a kernel panic. I repeated the above after reinstallation of ext2fsx, same behaviour. Below my panic.log and parts of the system.log just before the crash.
panic.log:
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Sun Sep 2 20:21:43 2007
panic(cpu 0 caller 0x56357C07)...
2007-09-03 03:46:24 UTC in Mac OS X Ext2 Filesystem