When I type text in the Notes field and then click out of the notes field, a space opens up under the title of the item in the spreadsheet. It is as if the note is being displayed under the title, but the text has no color. (The extra space under the title is even proportional to the size of the Note.)
Do you have Notes displayed as a column in the Spreadsheet?
I was able to reproduce what you were seeing, however it only happened because I had Notes displayed as a column, and the text was long enough that it uses multiple lines. Therefore the spreadsheet row height increases to accommodate this.
Oh man! Oh…ah…hmm…yes…I see it.
Oops 
Suggestion: If the row height is going to increase anyways, why not put the text from the note under the title? Or, let the user choose which field is shown under the title. (I do realize the row height increasing effect would happen no matter what cell had a bunch of text in it.)