From the Ubuntu Forum~
Xubuntu's File Manager (Thunar) does not support network / Samba browsing like Nautilus or Konqueror do. I found this out recently when I tried Xubuntu on an older computer (AMD 500 MHz / 128 RAM) and quickly switched (I found a few other features lacking). Apparently it's on the wishlist for a future version, but I needed it now. Kubuntu actually runs faster on it but that's another story...
Anyway as far as network shares, you have 2 options (aside from using the terminal to navigate):
1. Mount the network share locally so Thunar can see it as a "local" drive and you navigate to it (recommended). Here's (http://ubuntuforums.org/showthread.p...highlight=cifs
) a thread outlining how to do that (using cifs instead of smbfs).
2. Intall another file manager (like xffm4, Nautilus, etc.) that has network browsing capability. Here's (http://www.ubuntuforums.org/showthre...=xubuntu+samba
) a thread outlining how to install Nautilus in Xubuntu.
Method # 2 is not as efficient as method # 1 (you have to install a lot of the Gnome components required with Nautilus), but if you frequently visit different network locations where it's not feasible to mount them permanently using fstab, it may be better for you.
Hope this helps...