Problem in sending data to rest services from flex.

Hello Everybody,
I am working on an application in which I have to call rest services in the backend from Adobe Air UI in the front end, using as3 httpclient. Now, while calling these services I have to pass the data of a text file as an argument to that rest service.
What I have found is that, when I try to call the service by passing the data of a small text file, it works. But when I try to call the rest service by passing a huge data as an argument of a very big text file, it doesn't even reach till the service back end. It gives a warning of bad http request (error code 400) and also gives an security sandbox violation error inspite of putting cross doman xml file in the server root folder.
So I wanted to ask whether there is any restriction on the data size that can be passed to backend from as3 httpclient object to rest services.

Are you using a GET request? Servers often limit the maximum size of a GET request. Try changing over to POST.

Sorry, I forgot to mention that. It is POST request. I convert, actionscript model object which has to be passed as an argument to the service, into XML form and then I convert that XML into byte array using ByteArray class. Then I call post function of the httpclient class with 3 arguments i.e uri, byte array data and contenttype.

post(uri, byteArrayData, contentType)

here, contentType is "application/xml" and uri is the url of the rest service.