Guys, loosing the DB connections is usually due to errors in the shutdown sequence of Eclipse, it writes out the DB conncetion information as preference settings. If there are errors during shut down, then the settings are lost (very annoying).
Please try and restart Eclipse with the -clean command line option and see if that helps. If not, please post your Eclipse and MyEclipse version for us so we can help.
Also to perform a clean install we suggest redownloading the newest stable version of Eclipse SDK (3.0.1) and MyEclipse (3.8.4) and then installing them to a new location on your computer, then running them with the -clean option and pointing them at your existing workspace.
The -clean option tells Eclipse to rebuild its plugin cache, when you are trying to clean out old corrupt cache data, or pointing a new install at an old workspace, this is always a good idea.