This happens when you drag your fingers on or near the touch pad when typing. Sometimes the problem can be improved by making adjustments in the touchpad control panel. The best solution I have found, however, is to install the free utility TouchFreeze.
When I type on my laptop (Dell inspiron 1420) the curser jumps back to a prior portion of the paragraph and starts typing. This occurs constantly and drives me crazy. Any suggestions on how to fix it?