ios关于用json转字典问题

NSString *string1=@"{\"code\":\"1\",\"desc\":[{\"col_0007\":\"李玉华\", \"col_0023\":\"已回单\",\"col_0025\":\"800.00\", \"col_0027\":\"T14101400008\",\"col_0031\":\"2014-10-14 22:21:05\", \"col_0042\":\"null\",\"col_0057\":\"null\"},{\"col_0007\":\"李丽\", \"col_0023\":\"已转单\",\"col_0025\":\"0.00\", \"col_0027\":\"T14101400009\",\"col_0031\":\"2014-10-14 22:33:49\", \"col_0042\":\"null\",\"col_0057\":\"null\"}]}";
dicRoot = [[[SBJsonParser alloc]init] objectWithString:string1];
NSString *desc2 =[dicRoot objectForKey:@"desc"];
NSDictionary *dicRoot2 = [[[SBJsonParser alloc]init] objectWithString:desc2];
 NSLog(@"sucahkshdkahskdjh: %@", dicRoot2);

报错 Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayM dataUsingEncoding:]: unrecognized selector sent to instance 0x7a731320'