This is a problem indeed and has something to do with ICEFaces. We filed a bug report and will commit a fix as soon as possible. The only known solution on client side at the moment is not to let your session expire or to clear the site's cookies and the browsercache.
This is a strange bug which was not fixed until now, because a very simple workaround exists. If no path elements are showing up when browing particular properties, just exit the dialog and open it again. The second time it will work.
SPCP7 can support all databases which are supported by hibernate. All supported hibernate v3 dialects can be found here. To generate a Database Script for your database you have to checkout SPCP7 from scm and set it up according to the developer setup instructions in the root project. After that go to the spcp7-imagegallery-war project to the src/main/ant folder. There you can find the "build.xml" for the db-scripts generation. Adapt it to your needs and go to src/main/resources/afterwards/META-INF/persistence.xml afterwards. Change the persistence.xml to the appropriate dialect for your database and execute the maven "package" goal. When the goal finished successfully the new database script will reside below the folder you configured in the build.xml.
This can happen if you use maven from within Eclipse. Just click "Project" then Clean and then "Clean all projects", wait till completion and rerun the test with the jUnit plugin. It should work now.
We do not know the reason. This only happens when hot deploying again and again. So if you encounter this restart your server. After that everything will work as normal again.
If you deployed your project before and you hot deploy the war archive again Liferay reregisters the portlet. Libraries with the same name however will not be redeployed which means that your changes within these libraries will be missing. So either delete the libraries in the deploy directory of your server before redeploying or undeploy the whole image gallery before deploying it again.