2
Issue 1:
Try this. Go into the cache directory and delete everything but index.html. Make sure and delete adminmenu.php. When you then go into your admin pages, your site will regenerate the adminmenu.php. IT will indicate that you have not been into the admin home page before because it is regenerating the menu data before. MAKE SURE YOU BACK UP BEFORE DOING THIS...
Issue 2:
I suspect you uninstalled the module but you have one of several possible issues: In a module directory you have incomplete module files for the given module or you have only the module directory name with no files. The page load will show that error in module admin if you have module directories with incomplete module files, no files, or incorrect files for that given module. You can bank on it. Sometimes, when that error has occurred, it is because I inadvertently uploaded some of the module files to an incorrect module, or uploaded some of the module files without actually putting them into a directory.
How to fix?
Review each directory in ROOT/MODULES to make sure that only the files unique to each module are in that directory, that there are no files themselves at all in the ROOT/MODULES directory except index.html, and that the files in each directory only pertain that that module.
HTH
MMM...It tastes like chicken! ...