I'm using Windows 7 on a Dell Studio laptop. If I'm typing an email, the word I'm typing will suddenly appear in the middle,

[Rondeau]

Letters or words jump to another row or the subject line in email.

 

[COLGeek]

Sounds like you are bumping the touchpad, by mistake, and moving the cursor inadvertently. If you connect a mouse and disable the touchpad, does this behavior occur?