Displaying images?

Wondering if there is an issue with displaying images on TNL? I have noticed over the past couple of weeks that when using the string:

[img]jpg/gif/tif%20link%20here[/img]

That the images display when posting but after a couple of minutes the image doesn't display and instead just shows "image" on the thread.

I wasn't aware of anything like that happening, but I usually upload the image instead of linking to it, to avoid an unstable dependency.

Test image post: