IdentifyWidget - identifyTask.execute - HTTP Request Error

I created a simplified Identify IdentifyWidget. It contains a combobox for layer selection. After this widget is open, if I click a point on the map, an error message pops up after identifyTask.execute()

[RPC Fault faultString="HTTP request error" faultCode="Server.Error.Request" faultDetail="Error: [IOErrorEvent type="ioError" bubbles=false cancelable=false eventPhase=2 text="Error #2032: Stream Error. URL: file:///C:/identify?imageDisplay=1125%2C354%2C96&f=json&sr=102729&geometryType=esriGeometryPoint&returnGeometry=true&mapExtent=1150000%2C287000%2C1750000%2C475800&tolerance=3&geometry=%7B%22y%22%3A402600%2E00000000006%2C%22x%22%3A1482426%2E6666666667%7D&layers=top"]. URL: /identify?imageDisplay=1125%2C354%2C96&f=json&sr=102729&geometryType=esriGeometryPoint&returnGeometry=true&mapExtent=1150000%2C287000%2C1750000%2C475800&tolerance=3&geometry=%7B%22y%22%3A402600%2E00000000006%2C%22x%22%3A1482426%2E6666666667%7D&layers=top"]

However, after the widget is open if I click an item of the combox and then click a point on map, the tool works fine.

What's the possible solution for the HTTP request error? Thanks.