You have to decrease the size of the picture in Paint or such software. It's a real pain in the ass especially if you want to post few pictures.
If you are going to post them right from your phone through the app then it works just fine. I dealt with the same problem, I just post right form my phone instead coping to the computer than uploading.
Thanks for the tip. Works great. Would sure like to post up some past photos I have stored in my PC. Seems like I am missing a simple step here. I did notice the file size of the pic I just sent from my iphone is 378 KB, not the almost 3MB size indicated for same photo when trying to use the attachment page through PC. Wonder if there is a simple explanation.