An issue about NSUrlConnection

I met a weird thing with NSUrlConnection class, in my application i establish 2 connection, the first one get the data from my web server and the second one send a response message to server if the first one received the server's data.

This is the first connection part:
NSMutableString *ask = [NSMutableString stringWithString:@"act=ask"];
NSMutableString *askRequestString = [NSMutableString stringWithString:server];
[askRequestString appendString:ask];
NSMutableData *askMetaData = [self getMetadata:[self tableIds]];
NSMutableURLRequest *askRequest = [self generateRequest:askRequestString :askMetaData];
askConnection = [[NSURLConnection alloc] initWithRequest:askRequest delegate:self];
[askConnection start];
[[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:10]];

This is the second connection part, it is the same as the first one:
NSMutableString *report = [NSMutableString stringWithString:@"act=rep"];
NSMutableString *reportRequestString = [NSMutableString stringWithString:server];
[reportRequestString appendString:report];
NSMutableData *reportMetaData = [self getMetadata:data];
NSMutableURLRequest *reportRequest = [self generateRequest:reportRequestString :reportMetaData];
reportConnection = [[NSURLConnection alloc] initWithRequest:reportRequest delegate:self];
[reportConnection start];
[[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:10]];

The first connection is always going well, problem comes in the end of second connection, i check the response of the second connection by using this method:
(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response

when the statusCode return 200, i cancel the second connection. But i get these message in the console:
Loading program into debugger…
GNU gdb 6.3.50-20050815 (Apple version gdb-960) (Sun May 18 18:38:33 UTC 2008)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "i386-apple-darwin".warning: Unable to read symbols for "/System/Library/Frameworks/UIKit.framework/UIKit" (file not found).
warning: Unable to read symbols from "UIKit" (not yet mapped into memory).
warning: Unable to read symbols for "/System/Library/Frameworks/CoreGraphics.framework/CoreGraphics" (file not found).
warning: Unable to read symbols from "CoreGraphics" (not yet mapped into memory).
Program loaded.
sharedlibrary apply-load-rules all

And my application comes freezed, but it doesn't happen every times, that's why i think it's weird, have anyone met this issue?