One firefox can load webpage, the other cannot

Question

I have two Firefox running concurrently, one on laptop and one on desktop, both through the same router and ISP.
Last night the desktop would not load a particular webpage, a forum, but was fine with everything else. I assumed the problem was at the other end, it has happened before, and they would fix it.
I happened to try it on the laptop and it loaded OK, but I then found that the desktop version would still not load. Repeated tries confirmed this. The desktop has version 29.01 and declared up to date.
Wierd

Answer 1

On the Firefox that won't load the page, do you get an error that the page was not found, or it loads blank, or what happens exactly?
If the site is loading incompletely/incorrectly, did you try the usual?
When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.
(1) Bypass Firefox's Cache
Use Ctrl+Shift+r to reload the page fresh from the server.
Alternately, you also can clear Firefox's cache completely using:
"3-bar" menu button (or Tools menu) > Options > Advanced
On the Network mini-tab > Cached Web Content : "Clear Now"
If you have a large hard drive, this might take a few minutes.
(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, try either:
* right-click and choose View Page Info > Security > "View Cookies"
* Alt+t (open the classic Tools menu) > Page Info > Security > "View Cookies"
In the dialog that opens, you can remove the site's cookies individually.
Then try reloading the page. Does that help?
To see whether it's likely to be a settings issue, could you do a two-minute experiment?
'''Create a new Firefox profile'''
A new profile will have your system-installed plugins (e.g., Flash) and extensions (e.g., security suite toolbars), but no themes, other extensions, or other customizations. It also should have completely fresh settings databases and a fresh cache folder.
Exit Firefox and start up in the Profile Manager using Start > search box (or Run):
firefox.exe -P
Any time you want to switch profiles, exit Firefox and return to this dialog.
Click the Create Profile button and skip the option to choose a nonstandard folder location. Then start Firefox in the new profile you created.
Can you get into the forum in the new profile? If so, that implies there is an issue with a setting or extension in your regular profile.
When returning to the Profile Manager, you might be tempted to use the Delete Profile button. But... it's a bit too easy to accidentally delete your "real" profile, so I recommend resisting the temptation. If you do want to clean up later, I suggest making a backup of all your profiles first in case something were to go wrong.