The initializers for XMLGenerator are autoreleasing the XMLString they create. This should lead to a crash eventually. Also, initWithString: is calling [super init] twice. Here are the corrected methods.
 
-(id)initDefaultAtomHeader{

if(self = [super init])
    XMLString = [[NSMutableString alloc] initWithFormat:@"<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>"];
return self;

}
 
-(id)initWithString:(NSString *)xmlstring
{

if(self = [super init])
{
    XMLString = [[NSMutableString alloc] initWithString:xmlstring];
}
return self;

}
 
 
-(void)dealloc{

[XMLString release];
[super dealloc];

}