Dot-PNG file pasted in Excel slows down the spreadsheet a lot!!!

I opened a small dot-png (graphics) file in Notepad, placed it on clipboard then pasted it (values only) in a single cell.

The spreadsheet slowed down to a crawl!! Here she is...

2012.08.31...Excel with PNG very slow.xls

1 - I double-clicked the png-cell to select some of it.
2 - It took me about ten seconds before I could actually do the selection.
3 - Repeat the above in a test cell in the same file with as many chars as the png-cell.
4 - The spreadsheet reacted as it should. I could make a selection right away!
5 - Also, just trying to quickly select a rectangle of, say, 12 x 12 cells right under the png-cell and the selection cannot keep up with the mouse!
6 - The file is also blotted and very slow to calculate.
7 - The size should be approx 15.5 + 29.0 + 29.0 = 73.5 Kbytes.
8 - The actual size is 120,320 bytes.
9 - 73,934 bytes too long.

Anybody has any idea what's going on and how to work around it?

Thx. in advance!

danleonida-at-yahoo-dot-com