Recently we had one site built on Magento eCommerce system and I had to move the whole site to another domain and hosting. So I just copied all the files, exported database, set the connection in /app/etc/local.xml and changed secure and unsecure web path in table core_config_data.
Everything worked fine, except there were problems with Magento Connect Manager and instalation of new modules. Some modules just installed themselves alright, some of them wrote they installed ok but they didn’t appear in the menu the way they should (like Shop by manufacturer/brand/character) and some of them just reported errors while installing.
A little by fortune I discoverred the problem and the solution. There is an .ini file in magento, that keeps information of server paths, where the modules should be installed. So if you experience this kind of bugs and strange behavior, just delete the file /downloader/pearlib/pear.ini (maybe you can backup it, but don’t worry, magento will create a new one imediatelly). This should help.