Win 7 Machine Doesn't See or Won't Connect to Computers on Network

Current I have my main desktop PC, an HTPC hooked up the the tv in the living room, and I just finished building an unRaid server to store all of my media files.

My HTPC (running windows 7 home premium) sees everything fine. It can connect to the server as well as my desktop PC. The same is true with my laptop (macbook pro) and my girlfriends iMac

My desktop, however, doesn't want to play nice with the network. It sees my HTPC, but when I try to connect to it I get a "Windows Security" prompt that, despite entering the password to my HTPC, won't allow me to connect to it (says "Login failure: unknown user name or bad password" )

My desktop doesn't even see the server. It did briefly last night, but whenever I tried to open it I got an error code of 0x80070035 "Check the spelling of the name. Otherwise, there might be a problem with your network." I was getting the same error message this morning when trying to connect to the HTPC, but then I did something (I don't really know what to be honest), and now I'm getting the windows security prompt.

Everything is connected to the same workgroup. I've disable firewall and AV on the two windows machines. Networking stuff is really not my forte, and I don't even know where to go from here.

Thoughts?

try connecting to the server by IP address. IE Run command \\192.168.0.102\Share_Name

if I use the explorer and navigate to the server's ip (i.e. \\10.0.1.21), I can access it. But under the Network directory, where "TOWER" is showing up (that's the server's name...it's now showing up there again), I can't access it (I get that 0x80070035 error)

Disabling Windows Firewall fixed this issue. I could go back and figure out which setting in particular was causing this, but there's no real reason to have it turned on on the HTPC anyway so...