Only the first one is relevant. Your session failed to open a connection to the database (which it does everytime you open a page). The reason for this in most cases is that the mySQL server is overloaded temporarily and runs out of resources to grant another connection. Temporarily being just a fraction of a second in most cases.
As mySQL isn't a relational database, it requires manual maintenance at a regular basis. If not then small problems like these become big ones <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
