Sys.WebForms.PageRequestManagerParserErrorException: The Message Received From The Server Could Not Be Parsed?

I am getting the following error using an update panel with a gridview.
Microsoft JScript runtime error:Sys.WebForms.PageRequestManagerParserErrorException:
The message received from the server could not be parsed.Common causes for this error are when the response is modified by calls to Response.Write(),response filters,HttpModules,or server trace is enabled.

I have looked at all the "fixes" for this and none of them seem to be working.It works just fine on page load but when I click my async button,One row of the grid processes(I can look in the javascript debug) but after the firstrow is processed,I get the above error at this line.

try {
_this._webRequest.completed(Sys.EventArgs.Empty);
}
finally {
if (_this._xmlHttpRequest != null) {
_this._xmlHttpRequest.onreadystatechange = Function.emptyMethod;

[code]...

I am completely stumped here,
Here is my AJAX Response from FireBug

14008|updatePanel|ctl00_ContentPlaceHolder_UpdatePanel1|
<table border="0" cellpadding="2" cellspacing="0" width="100%" id="Table3">
<tr>

[code]...

What I do in this code is convert a BLOB value from a database and store it in a string in a custom object.What seems to be happening is that there are odd characters being put at the end of the string.Here is what I am doing to convert the data

byteBLOBData = (Byte[])(row[3]);
row["data"] = System.Text.Encoding.UTF8.GetString(byteBLOBData);

[code]...