Here's an easy option worth trying, that's the same but different.
It still uses postimage.org, but you are using that website directly, and not linking to it through Mayhem. The best bit is that there is still no need to register, or login to use it.
1) Go to
www.postimage.org website homepage directly.
2a) Select 'Browse' for suitable image(s) up to 5Mb. (jpg, png, gif, bmp, psd, tiff)
2b) Use the 'Resize facility' if necessary, select 'Family Safe', and 'Upload It'
3) 'Uploaded Completed' page appears. Scroll down and select 'copied to clipboard' button next to
Hotlink for Forums (1) - When '
Copied!' appears, paste into Mayhem reply for fullsize image.
Easy-Peazy Lemon Squeezy - if it works...
Andy