在iPhoneSDK中检测到uiActivityIndicatorView?(从uikit崩溃)

我从iTunesConnect收到以下崩溃报告。是否对uiActivityIndicatorView进行了调试?

Date/Time:       2009-09-26 12:33:02.034 +1000
OS Version:      iPhone OS 3.0 (7A341)
Report Version:  104

Exception Type:  EXC_CRASH (SIGABRT)
Exception Codes: 0x00000000, 0x00000000
Crashed Thread:  0

Thread 0 Crashed:
0   libSystem.B.dylib               0x31d54964 lstat + 8
1   Foundation                      0x3055baf6 _NSFileExistsAtPath
2   Foundation                      0x3055f6a2 -[NSFileManager fileExistsAtPath:]
3   WinterBoard.dylib               0x0019f034 0x19c000 + 12340
4   WinterBoard.dylib               0x001a032c 0x19c000 + 17196
5   UIKit                           0x30972650 +[UIActivityIndicatorView _loadResourcesForStyle:]
6   UIKit                           0x30972498 -[UIActivityIndicatorView setActivityIndicatorViewStyle:]
7   UIKit                           0x309723bc -[UIActivityIndicatorView initWithFrame:]
8   UIKit                           0x30a113f8 -[UIActivityIndicatorView initWithActivityIndicatorStyle:]

下面是我创建它的方法:

UIActivityIndicatorView *act = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
act.center = CGPointMake(160, 190);
[act startAnimating];
[self addSubview:act];    
[act release];