Image Resize Filter is an fantastic tool for giving content administrators the ability to place and resize images within rich-text editor-enabled fields. The genius behind this module is that it is actually a Drupal input filter that resizes images on the fly based on what the user does in the rich-text editor.
Keep in mind that it isn't just resizing the image for display, it is actually creating a new imagecache preset and saving a resized copy of the image for display. If that wasn't cool enough, it can also resize images from other sites and save the resized copy the same way. For content admins who require exacting control of their image placements and sizes, this is super.
Anyway, enough gushing - the point of this tip is that things aren't so rosy when the content administrator is using Safari as their browser. Safari has some known issues with rich-text editors in general that make it impossible to select the image within the rich-text editor to resize it.
So, the bottom line is this; if you want to use the Image Resize Filter, don't use Safari.
Is this a problem with Safari 3, 3.1 or 4?
Personally, I saw it with Safari 4, but in my research on the subject, I found that Safari's support for rich-text editors, in general, is a bit buggy.