Any time you paste a paint object into another environment, it will be pasted in with a surrounding frame. When you paste a paint object into a word processing document as an inline character it will have a frame around it. In line characters are not considered objects, and as such, can't have their fill or pen attributes changed.
The easiest way to work around this is to copy and paste the paint object into a drawing document first, change the pen pattern to transparent, and then copy and paste that element into the word processing environment.
Another method would be to paste the paint object on top of the word processing document by choosing the pointer tool from the status bar before pasting. Then change the pen pattern to white or transparent and then cut and paste the object into your document.
The above information also pertains to the limitation of changing the frame of any other object (ie - spreadsheet frame) once it is pasted into a word processing document as an inline character.