I recently upgraded my ZendServer (development) from 5.0 to 5.6.0. This includes PHP 5.2.17 and 5.1.50. Everything worked very smoothly, but when I restarted my machine MySQL failed to start (Error 1067). I googled my way to this post, then found the .err file in MySQL's /data directory:

InnoDB: Error: log file .\ib_logfile0 is of different size 0 45088768 bytes
InnoDB: than specified in the .cnf file 0 56623104 bytes!
120425 10:28:26 [ERROR] Plugin 'InnoDB' init function returned error.
120425 10:28:26 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
120425 10:28:26 [ERROR] Unknown/unsupported table type: INNODB
120425 10:28:26 [ERROR] Aborting
120425 10:28:26 [Note] C:\zend\MySQL51\bin\mysqld: Shutdown complete

I changed the logfile size back to the old value:

# Size of each log file in a log group. You should set the combined size
# of log files to about 25%-100% of your buffer pool size to avoid
# unneeded buffer pool flush activity on log file overwrite. However,
# note that a larger logfile size will increase the time needed for the
# recovery process.

and the server restarted happily. This was a slightly annoying bug, but in fairness the ZendServer installer (Windows 7) did a great job of preserving the old config (my 2011-03-31 1137.ini.bak) which made rolling it back the bad setting easy.