I have this code here:

NSString *post = [NSString stringWithFormat:@"deviceIdentifier=%@&deviceToken=%@",deviceIdentifier,deviceToken]; 
NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:NO];
NSString *postLength = [NSString stringWithFormat:@"%d", [postData length]]; 
NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] init] autorelease]; 
[request setURL:[NSURL URLWithString:@"http://website.com/RegisterScript.php"]]; 
[request setHTTPMethod:@"POST"]; 
[request setValue:postLength forHTTPHeaderField:@"Content-Length"]; 
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"]; 
[request setValue:@"MyApp-V1.0" forHTTPHeaderField:@"User-Agent"];
[request setHTTPBody:postData]; 
NSData *urlData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil]; 
NSString *response = [[NSString alloc] initWithData:urlData encoding:NSASCIIStringEncoding]; 

which should be sending data to my PHP server to register the device into our database, but for some of my users no POST data is being sent. I've been told that this line:

NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:NO];

may be causing the problem. Any thoughts on why this script would sometimes not send the POST data? On the server I got the packet trace for a failed send and the Content-lenght came up as 0 so no data was sent at all. Thanks for any help