Can't access most of my network

I'm running Win 7 64 bit system with a Synology server & I have the latest version/build of TI installed. Synology automatically creates a "home" subdirectory (which I map as my H:\ drive) & I can back up & access this folder just fine. However, every other subdirectory on my server can't be accessed, even to just back it up (for example, I have a folder called Shared that I map as my N:\ drive that I have full read/writes to that I can't back up). I keep getting the "Edit Authentications" box in my face, and I've tried using both my user id/password as well as the user id/password for the Synology box and the connection fails & fails & fails. I'm going blue in the face trying to fix this! I can read/write to the mapped drive just fine within Windows. Please help!!

CORRECTION!! I think I used to be able to access the "home" subdirectory using TI; now I can't. (Sometimes I get the Edit Authentication box, sometimes the "Windows Credentials" box. However, I CAN back up my local "C:\" drive to an external hard drive that directly attached to my Synology box. Since I can't get TI to work with my NAS directly, I'm also using this ext. drive to use Synology's own "Local Backup" to back itself up to the ext. drive. I haven't upgraded to Synology's newer operation system DSM 3.0 (I used DSM 2.3) because I thought I had read that there were problems with it & TI.