I have just the same problem it seems. I use the WLHDD for scheduled backups, but sometimes in the middle of these it will disappear from my network. The backup software will say it cannot find the path to it, and it no longer appears under My Network Places. The only thing I can do to get it back is to reboot the device.
This does appear to happen in the middle of big writes, so if I've made large changes to my drive the backup will fail. Sometimes this will corrupt the backup and I'll have to erase and redo the whole thing. On one occasion it refused to write to the disk, and I had to reformat the partition!
I tried rolling the driver back to 1.2.3.0 but it made no difference.
I do these backups over WiFi. The connection does not appear to be broken however, so the problem does appear to be internal to the WLHDD.