I use firefox & have no problems with posting images either. I am on Windows xp.....changed over to firefox awhile ago....only thing I don't like about firefox is that I can be running & doing nothing & all of a sudden, firefox takes my cpu usage up to 100%.....I am dead in the water while it's stuck doing that......sometimes I have to end up shutting my whole computer down just to get control back.
did the Ctl/alt/delete to see what processes were running....that was when I saw the firefox at the 100%....strange.
I also pick up pictures from photobuket....easy to pick up the address of the image......however if you pick up more than just the part starting with the
http://......., it won't show up if you use the image insert at the top of the posting.....When I pick up an image address that already starts out with the

then I just past that directly into the message & that gives me the image. If you have to many of the controls, or the wrong ones, the image won't show up either.
Just a thought?.....found that while I was experimenting & trying to figure out how to post images.....many failures also while trying to figure out just the right combination.
Keep experimenting.......when you pick the properties off the right click....you have to pick up the whole "address" & then cut that & past it into the "insert image".
Know you will figure it out....it does work with firefox...just getting familiar with it is difficult
good luck,
Debbie