This is rather confusing.

We had 2 kinds of sporadic error in the error log, which presumably were issues on photobucket's end. These seem to have stopped.

I couldn't reproduce it freezing as described.

However, I did reproduce it not working. The photobucket image link in my test post was broken, because Composr was prepending the base URL onto it. I think I accidentally caused this when rolling in other fixes to your site, when I did the big update. This is now fixed.

See my test post: http://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=moderation%2Ftest&redirected=1#post_1448156

Sorry for spamming your photobucket account with my test images ;-).

No worries on the spam Chris !

I noticed the original issue on an iPhone 5, but ran out of time to follow it up.
I got an iPhone 6+ this week and noticed the same issue.

I just tried again after your fix on the 6+ in Safari and it does not work for me :-(
If I use Chrome on the same device it work find and it works fine on my laptop for Safari.

So it appears that there is still a problem with iPhones running Safari.
I tried clearing the cache, but it made no difference.

When you get a minute can you try it as well please.

Cheers
Ade

I was able to have it work on both iPhone Simulator (iPhone 6, iOS8) and my physical device (iPhone 5, iOS7). Upload did take a while and was about 0.5MB for a proper picture. It could be that a mobile connection stalled and broke the process for you, as that is a lot of data for an unreliable connection to transfer over HTTP. I looked to see if there is an easy way to tell iOS to use a lower resolution upload, but there isn't (not directly).