I ran into a similar scenario (EZServe does not recognize default username/password) at least twice during my EZSrve 2.0X adventures over the past few weeks. If I remember correctly I had to use both the TFTP solution (make sure you turn off Windows firewall) to reimage the firmware AND a hard reset to restore the FLASH defaults after that, but you might try a hard reset (i.e. paperclip in the reset hole on the EZSrve) first as my guess is username/password information is stored in the FLASH memory.
With regard to X10 devices, I have been able to make X10 devices work in both directions using the 2.03 firmware (i.e. as a device trigger in a condition and as a responder in an effect). The important thing is to use the X10 hex codes for device status in the status fields (i.e. 0x02 for on, 0x03 for off, etc.)
I haven’t tried turning an X10 device on/off directly through the HTML interface but will do that when I get home tonight.