The paypal logos wouldn't cause it. Website text and pasting text in from Word can. It sounds like you have RTF in the Inventory item description fields. Duplicating an Inventory Item also duplicates teh RTF too.
The only way to get rid of it, is to a) totally delete all of the description field text and Post changes prior to duplicating an old Inventory item b). strip out the RTF prior to duplicating. Meaning to go through the description field and delete all the slashes and other code you can see, post changes and then duplicate
It is preferrable to do the first option. Once you fix it by removing the RTF from the description field, the problem should stop.
We had this same thing happen to us once. It was maddening until we figured it out.
Re: Description went wacky