This is an issue with some 2.4.x versions where searching on integer/autonumber values fails because the XAS adds a .0 notation (which obviously isn't correctly handled as integers and autonumbers normally do not have any decimal numbers). For example, an integer value of 2009 in a search field will be converted to 2009.0 on searching, which isn't a valid integer value and thus the error message.
I believe this was on the fix list for 2.4.5 which was released yesterday. But I have not yet verified whether or not this particular issue has been resolved in 2.4.5.