Sys.ParameterCountException: Parameter count mismatch
Thats what happens when you call a public method of an ajax API with the incorrect number of parameters. For example, try Boolean.parse("true", "what?"). It only takes 1 parameter, you passed in 2 or your sending a null value.
also your submit link ...../RequestList.aspx does not look like a proper address.so make sure you are not passing null or wrong parameters.
Possibly worth wrapping your data: item in quotes
data: action = 4becomes
data: "action = 4"
setting debug="false" in de web.config seemed to remove the error