It seems a couple of options were missed when you compile for the targets "MCB2300 Debug" and "MCB2300 RTX".
In options for the file LPC23_EMAC.c, properties tab, set Zero Initialized Data and Other Data to IRAM2 [0x7FE00000-0x7FE03FFF].
Cheers Dave
WOW! For already about a month I am trying to figure out why it sends only frames consisting of 1366 0x55 bytes! This was a problem. Thanks!