Meanie's site is full of useful information.
If you install a package in Cacko/Sharp and get the above message, just uninstall it, then open a console and install it this way. Then you'll get more useful messages as to what the dependencies are.
ipkg install /home/Documents/Install_Files/packagename.ipk
Your path to your new package may be different, just change the path accordingly.
Another method to find dependencies, is to search the forum, or find a feed that has the same package and download the "Packages" file.
The "Packages" file is just a text file and should have a description and dependencies listed for your package.
If you use Windows to try to read the "Packages" file, just open it in wordpad, and copy/paste it to notepad and save as Packages.txt
Wordpad will convert the utf8 text formatting to something you can read in windows.