Please try enabling the Load on startup option under, Settings>>General>>Application, and if no better, or it is already enabled there, disable it, click, File>>Exit to close the program, re-enable it, then click File>>Exit again to close Mailwasher Pro.
Restart your PC and see if that helps.
If no better, please try adding a shortcut to Mailwasher, (drag and drop from your desktop using the right mouse button) to your startup folder under, Start>>All Programs>>Startup folder.
If still no good, the usual other reason it wont load on startup is that is is set to run as admin from either the shortcut in the startup folder, or the programs .exe file itself...
Locate and right click on these, click Properties, and ensure that nothing is ticked under the Compatibility tab.
(Note this is for Vista and up only, NOT XP)
If no better, disable the load on startup, click OK to save changes, then file>>Exit to close MWP, restart it and re-enable it then click file>>exit again and see if that helps....
If still not, click Start, search for msconfig and click msconfig.exe.
Click the startup tab, and ensure that MWPro is checked (if there).