I have following error msg in console when using NSThread "Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now..." I have submit my sample code here - (void)viewDidLoad { appDeleg = (NewAshley_MedisonAppDelegate *)[[UIApplication sharedApplication] delegate]; [[self tblView1] setRowHeight:80.0]; [super viewDidLoad]; self.title = @"Under Ground"; [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; [NSThread detachNewThreadSelector:@selector(CallParser) toTarget:self withObject:nil]; } -(void)CallParser { Parsing *parsing = [[Parsing alloc] init]; [parsing DownloadAndParseUnderground]; [parsing release]; [self Update_View]; //[myIndicator stopAnimating]; [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; } here "DownloadAndParseUnderground" is the method of downloding data from the rss feed and -(void) Update_View{ [self.tblView1 reloadData]; } when Update_View method is called the tableView reload Data and in the cellForRowAtIndexPath create error and not display custom cell - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; CustomTableviewCell *cell = (CustomTableviewCell *) [tblView1 dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { [[NSBundle mainBundle] loadNibNamed:@"customCell" owner:self options:nil]; cell = objCustCell; objCustCell = nil; }