DW CS4 Ignoring Check In/Out on 1 Site Suddenly

Question

We're using Dreamweaver's Check in/out functionality in my office and have been for about a month now. No problems.
Suddenly this morning, my coworker's DW is not checking out the files when she opens them. It sometimes throws a prompt that the file is read-only and gives the options to View/Make Writable, and sometimes it asks her to overwrite her local copy (yes), and sometimes it doesn't say anything at all. Regardless, once the local file is opened, it does not show up as checked out, nor does it offer the option (when right-clicked) to check out or check in.
Exactly how it happened:
She arrived this morning, checked out a local file to make changes, checked it back in like normal (which Puts the file to our remote live site), and the changes appeared on the remote site as expected. Needing additional changes, she then Checked Out the file once more and proceeded to make substantial changes. Upon saving the file, the changes were visible on our local site (as expected). But now her Check In option was greyed out, as are the Check Out and "Undo Check Out" options. She also does not see a checkmark beside the file indicating that she has it Checked Out, although I do see a red checkmark in my DW, indicating that the file is Checked Out by her. She can click the actions Get and Put, but they don't do anything. The dialog reads that the file gets Put to remote, but the remote server isn't reflecting the changes. Attempting a Syncronization, there is a prompt that says no sync is necessary. I tried to run a manual sync with this file's action set to Put, and still the changes are not showing up on our remote site.
She hasn't touched any of the settings since yesterday (when it worked  fine) and upon inspecting her settings, they all appear to be correct -  identical to mine (which still works) and to the other Sites we manage in the same way,  which still work for her (we tested them to see). So we're pretty befuddled as to what's going  on. Can anyone help? It's rather urgent.
Probably Important:
We just noticed that he site isn't connecting to the remote host. Again, all the settings are the same as mine. The power outlet icon is greyed out on her panel, but mine is working as expected (shows plugged in with a green light). She tried to click it to connect, and it did not respond or appear to make an effort of any kind. Her icon works for the other sites we manage, just not for this one. This happens to be our most active site.
One more thing: I duplicated her site in the Manage Sites dialog and tried the new copy - didn't work. Before you ask: yes, she has restarted DW and rebooted her computer.
She is running CS4 on WinXP and I am running CS4 on Win7.

Answer 1

Dreamweaver has an annoying habit of occasionally forgetting site settings. You may need to redefine the site again or actually create a new site definition in Dreamweaver (don't just duplicate it though) and see if that resolves the issue.