Exception on C# - but program still works

Question

Here's what's going on. I'm opening a file on FTP that exists using a WebClient. The file exists and the function has worked in the past, but now for some reason throws an exception. (System.Net.WebException: The remote server returned an error: (550) File unavailable (e.g., file not found, no access).). The funny thing is, the script still opens the file and does what it's supposed to. Has anyone ever heard of anything like this?

WebClient downloadRequest = new WebClient();
downloadRequest.Credentials = new NetworkCredential(pusername, ppassword);
byte[] downloadBytes = downloadRequest.DownloadData(purl);

Here's the stack trace:

[WebException: The remote server returned an error: (550) File unavailable (e.g., file not found, no access).]
System.Net.WebClient.DownloadDataInternal(Uri address, WebRequest& request) +287
System.Net.WebClient.DownloadData(Uri address) +106
System.Net.WebClient.DownloadData(String address) +29
ftp_connect.copyFile(String purl, String pusername, String ppassword, String pubordev) in d:\wwwdev\test\ftp\ftpconnect.aspx.cs:112
ftp_connect.copyFolder(String purl, String pusername, String ppassword, String pubordev) in d:\wwwdev\test\ftp\ftpconnect.aspx.cs:160
ftp_connect.Page_Load(Object sender, EventArgs e) in d:\wwwdev\test\ftp\ftpconnect.aspx.cs:93
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
System.Web.UI.Control.OnLoad(EventArgs e) +99
System.Web.UI.Control.LoadRecursive() +50
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627

Answer 1

It turns out that I was calling a function which called the function I was trying to get to.

So, the solution I guess was to look at the stack. Should have done that first.

Answer 2

Presumably the file is there from a previous successful run?

Answer 3

The script might be using a version of the file saved when the Web request was still working.

Answer 4

Maybe the file is in user by some other client/user.