Cannot Log Into Server with Remote Desktop Connection

[Variscite]

I cannot log into our 2008 Server via Remote Desktop Connection anymore. I put in the correct IP address and arrive at the server logon, but all logins fail. All the logins work face-to-face on the server and I can get in with logmein, but not with Remote Desktop Connection. The error is: The user name or password is incorrect.

I totally removed antivirus and software firewalls from the server while I am trying to troubleshoot this.
All the user logins I try are in the RDP Access group and Remote Desktop Users group on the server.
On the Remote tab in System Properties, Remote Desktop section "Allow connection from computers running any version of Remote Desktop (less secure) is checked.

Error log shows: An account failed on logon: Event ID 4625. I'm researching this, but so far nothing that I have found applies.
RDP in the router is forwarded to the server's IP address. The router is Cisco/Linksys BEFSR41. Any suggestions?

 

[Variscite]

Forgot to add - this problem is when using Remote Desktop Connection from outside the LAN. Using Remote Desktop Connection within the network works.

 

[PWise]

try using
domain\username

 

[Variscite]

Thanks PWise for that suggestion. I just tried it and it didn't work.