[SOLVED] "The Jazz Session" widget changes the font size of the whole site!

I installed WP Custom Widget and activated it without problems. I wanted to put a widget for "The Jazz Session" podcast on the sidebar so I followed their instructions and pasted the code provided HERE into the WP Custom Widget window. I had done this previously with other code without any trouble. Although the widget itself was displayed alright, it changed the font size in the whole website: header, titles, body, every text appeared in a significantly smaller font size.

I'd really like to post this widget, which will get my site mentioned in the The Jazz Session. I have seen this widget displayed in several other sites without any apparent problems (for example, see HERE and scroll to the bottom of the page), so I assume there must be some incompatibility with Atahualpa. Could anyone help, please? Thanks very much!

Edit: The same happens using the "My Custom Widgets" plugin. You can see what I mean looking at these screen shots of the site: BEFORE adding the code and AFTER. The Jazz Session widget appears at the lower right corner. Compare the two to see the dfferences in font.