After Mavericks upgrade – problems printing large custom page sizes turned out to be caused by corrupted PS6 preference file. After much research (mostly not on this site) I found that removing Adobe Photoshop CS6 Prefs.psp solved the problem. It was NOT the Epson 3800 print driver. This was not an intuitive solution, but what a relief! I have saved my corrupted file if anyone wants to check it out.