Mike,
Invision Power Board has had problems with the Blog and Gallery add-ons and the uploading of images. The problem is with the php and how much memory is used. As they have told me "there is a find line between it working and not". The server I have hosting my site has plenty of memory but... I still see this error at times. There are several ways we can get around this.
I have not had any problems with my Blog and attaching images because I "hot link" them from a "dir" on this site. I simply upload them to a place on my site and them link them in the Blog. Simple. This will also work for other members of this board.
In order to link your images they must have an address on the net. i.e.
"http://www.rktman.com/rlh/images/jollyjay.jpg" You can add images to your Blog in this way as you add images to posts.
Having the web address you can link as you wish, provided you have rights to the picture.
If you do not have a way to upload your images to a server yourself this can pose a problem. My fix to this is to allow those members who want space for their images for their Blogs space on the Model Marina server. Although I WILL NOT grant anyone FTP direct to the server, I will upload the images for you and provide you with the needed address. If anyone would like to do this, just send me an email.