This is a common problem among users. The way Poser locates textures (and objects) is a bit obscure and it is very easy to make (very small) mistakes.
There are two ways to correct the problems.
Firstly it possible to simply save back any failing prop after you have loaded it and helped Poser to find the missing elements (this will generally fix the problem) but this is a lot of work as you will have to take care to maintain the link between the icon and the file and you must make sure the whole prop. Keep in mind that in most cases files contain relative references, you can always replace them with absolute references (Poser does understand these although it would never use one itself). Another thing to remember is that Poser is very sensitive to exact file names, far more sensitive than the OS tools (even on a Mac).
The second way would be to use one of the tools to correct the references (i did notice you're working on a Mac and most tools are only available for the PC).

If you find a tool for the Mac I do advise you to get it and use it. It remains surprising how many incorrect references exist (even in the core Poser content).