img_assist does not create the img tag ('HTML code' insert mode)

I'm working on the upgrade from Drupal 4.7.4 to 5.1 on my testsite and I initially couldn't get img_assist going. Both with TinyMCE and a normal textarea, everything seemed to work fine, until the moment you click the 'insert' button. The 'img' tag was missing from the generated HTML.

So I started debugging the code and found out that img_assist_display() received a size label 'Thumbnail' (so with capital 'T'). The images in the node had an entirely lowercase size label. So I added a strtolower() to line 1055 and that fixed it for me.

It is a hack though. But hopefully this info helps the maintainer to find the root cause. I'd be happy to assist with more information :-)