If you continue to have trouble with this, you may want to reassign the jump action to another key in the options menu or disable the sticky key feature in Windows.
To do this:
1. From the Windows XP desktop, press the Shift five times in a row to bring up the sticky keys option box.
2. Click Settings, and under the sticky keys heading, click on Settings.
3. Uncheck the 'use shortcut' box to turn off this feature. Click Apply and OK to save the setting.