well found. wont the page that was being linked not get much PR anyway, as it has a unique query string for each URL???
If you add nofollow to the link for prtool.info, you are violating the terms of service for the free pagerank tool. I'm not happy seeing you suggesting this "fix". You are completely free to remove the PR images altogether, but I ask you to please not follow the instructions from the OP folks. All other images for social bookmarking sites are hosted on your directory - prtool hosts and dynamically serves every single PR image. If this "leaking pagerank" subject is an issue I guess we'll just have to remove PR images from the default install.
See Tekime, why can't there be a database store system n an internal PR system for PR check? The script is fine, is improving, you are doing great with it, but then installing 3rd party script into it is not done. Your script is gr8, but atleast provide something which is stable, pure and clean. Why should I pass PR juice to someone else in my site, think this way!
By v1.6 or so I'll probably get PR functions built-in but it isn't just a matter of slapping it in there if I want something that works well. I think everyone can agree that a quality script is ultimately better than a bunch of messed up features. For the next update I'm just going to remove them by default and provide instructions on adding the images since there were many requests for them.