This article suggests that Greek striker/winger Angelos Charisteas thinks the Chicago Fire aren't willing to pay him enough. The website itself looks a little sketchy but there's some detailed information. A loose translation:

Shortly after Christmas, a spokesman for the Chicago Fire contacted Panetolikos suggesting a two-year contract with annual earnings around 600,000 euros. Almost twice as much as what he receives from his team.

The article says Charisteas said no to the offer. There's a couple of complications with the report. First, that figure could include a transfer fee the Fire would have to pay. Charisteas is currently under contract with Greek club Panetolikos until July 27, 2012. If this rumor does indeed have legs, Charisteas is a name to keep in mind as a summer signing. MLS generally does not pay transfer fees and if the Fire can pick up Charisteas in six months for free, there is a lot of motivation to simply wait.