I don't know why it just started doing this now, but I can't seem to get it to stop. Whenever I try to view a thread, I get a '500 Internal server error'
../modules/newbb/viewtopic.php?topic_id=3&forum=5

It was working fine before but now for the past few days it's beein giving me this error. This only happens when I try to view a thread in the forum -- nowhere else. I deleted the newbb_thread.html file and replaced it with the default one to see if that was the problem, but it's still doing it. I haven't touched any of the php files when I was trying to customize my site.
I also installed the xoopsCare module and cleared out the cache and all that. I also cleared out the cache on my own computer but it's still not working.
Everything else on the site runs fine, so I don't think it's my site host... Is it something to do with queries, maybe? If so, how do I fix this?

It is an issue with your server/hosting company and you should raise it with them.

Howso? Because all of my other pages work fine with no errors.

EDIT: I contacted my hosting provider and they could not see what the problem was...

Is the default template active?
Did you update the newbb module in admin - module admin?
Are there messages when debug is on?

-I made a clone template of the default NewBB template like the instructions said. The clone template is the one that's active.

- Yes, I've updated through the admin. I even uninstalled it and re-installed it again to see if it would fix the problem but it didn't.

-I'm not getting any debug messages.