получение EXC_BAD_ACCESS при назначении NSString

Я написал функцию для возврата строки в путь к каталогу. Я получаю EXC_BAD_ACCESS, и я думаю, что эта функция является причиной. Нужно ли сохранять nsstring или что-то в этом роде?

-(void) getRemoteFiles:(NSMutableArray *) M
{
    [self createFileToAppDirectory];

    if (!networkqueue) {
        networkqueue:[[[ASINetworkQueue alloc] init] autorelease];
    }

    [[self networkQueue] cancelAllOperations];

    [self setNetworkQueue:[ASINetworkQueue queue]];
    [[self networkQueue] setDelegate:self];
    [[self networkQueue] setRequestDidFinishSelector:@selector(requestFinished:)];
    [[self networkQueue] setRequestDidFailSelector:@selector(requestFailed:)];
    [[self networkQueue] setQueueDidFinishSelector:@selector(queueFinished:)];


    int i;

    for (i=0; i<[M count]; i++) {
        NSString *url=[M objectAtIndex:i];
        NSString* theFileName = [url lastPathComponent];
        NSString *safestring=[url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
        if ([theFileName isEqualToString:@"nothing"]==NO) {

            ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:safestring]];
            //think this is causing the problem
            NSString *savepath=[self getDirectoryPathForFileName:theFileName];
            //[request setDownloadDestinationPath:savepath];
            [[self networkQueue] addOperation:request];
        }

    }

    [[self networkQueue] go];
    //error thrown after this point


}
-(NSString *)getDirectoryPathForFileName:(NSString *)filename

{
    NSFileManager *filemgr;
    NSArray *dirPaths;
    NSString *docsDir;
    NSString *newDir;
    BOOL isDir;


    filemgr =[NSFileManager defaultManager];
    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    docsDir = [dirPaths objectAtIndex:0];

    newDir = [docsDir stringByAppendingPathComponent:@"remix_data"];
    if ([filemgr fileExistsAtPath:newDir isDirectory:&isDir]==NO) {
        NSLog(@"dir should exist but does not... go funt dat");
    }

    NSString *localFilePath = [newDir stringByAppendingPathComponent:filename];
    [filemgr release];
    [docsDir release];
    [newDir release];
    return localFilePath;
}