Configuration Menu Items on Admin Page not working after 1.5.x upgrade

Upgraded from 1.3.9h to 1.5.0, working through several issues one of which is when I'm on the Admin Page and select any item under Configuration it takes me to the website. Need any information on how to fix this problem. Thanks in advance for any suggestions.

That's typically a result of using outdated PHP files that didn't come with v1.5.0. Either files you didn't upgrade, or didn't upgrade properly, or replaced with versions from old addons or from addons that weren't upgraded properly, or from incorrectly merging changes from old addons into new files.
There are several other discussions about the same symptoms, with the same cause.

Thank you for your information. I just wanted to let everyone know that this issue has been resolved. I took into consideration your above reply and also read other post by you, then followed up with going back through installation instructions carefully line by line and the issue was resolved. Most of the time I find when I have a problem with Zencart, it's not Zencart's fault, it's mine! Attention to detail is VERY important when changing, maintaining or upgrading.