Ever since I upgraded to FF 3.5, all of the buttons (edit, reply, new topic, etc.) on the GOG forums disappear on a semi-regular basis, perhaps 1 out of every 5 visits to the site. If I clear my history, they come right back, but it is only a matter of time before it happens again. So far, GOG is the only site it happens to. Are any other Firefox 3.5 users out there running into anything like this?

Nope, it's normal with me...

Your computer is made of crazy. I am rocking FFox 3.5, and no oddities are present on my end.

not so far (touch wood)
the FF3.5 change hasn't had any noticeable effect on anything that i use (so far).

Firefox 3.5 all okay here. Are you running plugins/add-ons that may be interfering?
And tested at work---
Fx 3.x = okay
Fx 2.x = okay
IE7 = okay
IE8 = okay

I thought of that, but I only run some very basic plugins that have never been a problem before 3.5 (AdBlock Plus, Fire.FM, GooglePreview and the Java Quick Starter). The only one that I could possibly see causing this would be ABP, but a lot of people use that, so I would think if it were the cause, my issue would be more widespreaad.
This whole issue is really odd. It is obviously connected to my browser history in some way, but it seems to only be the recent history. When I clear my history to fix the issue, I only have to clear the previous hours worth of history... hmmm... perhaps it is not something about the GOG site that causes this, but rather the site I visited before I came to GOG... I'm going to have to pay attention to that next time it happens.

Are you sure its not a connection issue? It seems that the buttons are the last element to load, I get capped to modem speeds every so often and thats where I've seen that happening for me (in IE8)

If that were the case, then simply refreshing the page would fix it, I wouldn't have to clear my history to bring the buttons back.

No, but i had a problem with the earlier Firefox version. Whenever i tried to use reply or new post buttons, absolutely nothing happened. And GOG was the only forum where anything like this happened, everything else worked fine.
When I updated to Firefox 3.5 GOG forum works perfectly with Firefox too.
Not that this has much to do with your problem, but it's Firefox specific problem with GOG forums anyway.

Unless it'sloading from the cache. Have you tried the shift F5 refresh (or whatever the full refresh is in FF)?

Yep, it does nothing, only clearing my recent history fixes it.

That's definitely a weird one. I have no issues with FF 3.5 on any of the sites I regularly visit. I have AdBlockPlus, NoScript, IE Tab, Ultrasurf Firefox Tool, and DownThemAll installed.

I haven't had any problems with GOG.com using FF 3.5. BUT, I've not been too happy with 3.5 either. It takes a lot longer to do things with 3.5 than it does with 3.0. Longer start-up time, longer time to access some websites. And sometimes (everytime I check my yahoo email) I need to refresh to get a webpage. I never had these kinds of problems with 2.xx and 3.xx. I hate to say it, but I think IE7/8 is better than FF 3.5.

Now that I have not experienced at all. So far, FF3.5 has been the exact opposite; immensely faster than any previous version of FF and infinitely superior to any version of IE I have used. The only issue I have is the buttons on GOG, which of course has not occurred once since I posted this.

This happened with me, but I think only since I updated Silverlight. It's been good lately though.