Epson Artisan 725 scanner works fine up to and including 600 dpi. Scans over 600 dpi (1200 etc) fail with 'communication error' from scanner. Works fine at all resolutions with Windows 7 (Virtualbox) The printer is networked (ethernet)
Not sure if this is a particular solution but 1200PDI is a lot my only thought could be sending that size of packet across an Ethernet network. In one continuous block. Have you tested it to make sure if works locally? Are there many devices in your LAN?