In field of type Notes - TextArea, data Input of a $ (dollar sign) followed by one or two digits between 1 and 9 will result in deletion of the numbers.

Here's how to replicate the problem.
1) Go to the demo site. Create a custom field of the Data and Input Field Type of Note and TextArea. I did this in an extension of the individual contact record.
2) go to edit the field in a contact either via the ajax option or the full contact edit
3) enter $1234
4) save your changes
5) check what's in the field. it wil. be 34 if the error is present.
Note, if you enter $00, the result in the field will be %5
This does not happen in situations where the $ is followed by a letter or other punctuation or space.
This did not happen in 4.2.9

The impact of this error is that users cannot write notes that have currency in them. It appeared in a field where users were documenting fundraising goals for potential donors.