Problem with images

Is it possible to add image file to an item and have it displayed without any complications? I followed all the topics re imagemagick path, incl. installation, macports, etc and I couldn't make it work at the end. Now, I get an error when I even try to add an image file to existing item. Does it depend on the theme I use? Should I uninstall the Omeka from my webspace all together and try again?
ANY help much appreciated.

Many thanks,

Have you changed the permissions on your "files" directory to make it writeable?

Thank you Sharon for such a quick reply. Yes, I have made the files dir writeable. I decided to install Omeka again and start fresh!
Is there any user-friendly guide how to tackle Imagemagick?