Unable to access networked drive, but able to access same unc path

I have a Western Digital My Book (World Edition) connected via nic to
wireless router. Have previously had no issues with mapped network drived
till i reformatted and reinstalled xp to my laptop. (Previously running xp).
system is exactly the same... only difference is that I have gone from AVG
Free antivirus to ESET Smart Security. I can map my network drived to the My
Book, all others work appart from one. But I can access the unc path without
issues.

Please help... going Grey and pulling out hair!!