Parse Issue in Xcode 4.6.3 - "Expected a type" - Can't find the error

Question

I have a Problem with Xcode:

At the moment I am working on an application for iOS SDK 6.1. Somedays ago I was implementing some methods and tried to compile the project. Then something strange happened:

Compilation failed and I got some errors (see picture below) in two files, which aren't related to the methods I worked on.

I searched for errors in my code but couldn't find any.
Then I closed the project and opened it again: They were still here.
Then I closed the project and Xcode and reopened both: They were still here.
Then I created a new project and copied all the code: The issue appeared again.

Now I am stuck and have no clue what to do. Do I miss something in my code?

Please help me!

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EDIT 1:

Here are some code snippets, which should show my code after I followed the suggestions of Martin R:

//  PlayingCardDeck.h  
@class PlayingCard;  
@interface PlayingCardDeck : NSObject  
- (void) addCard: (PlayingCard *) card atTop: (BOOL) atTop;  
- (PlayingCard *) drawRandomCard;  
- (BOOL) containsCard: (PlayingCard *) card;  
- (BOOL) isCardUsed: (PlayingCard *) card;  
- (void) drawSpecificCard: (PlayingCard *) card;  
- (void) reset;  
@end  

---

//  PlayingCardDeck.m  
#import "PlayingCardDeck.h"  
@interface PlayingCardDeck()  

---

//  PlayingCard.h  
#import <Foundation/Foundation.h>  
#import "RobinsConstants.h"  
#import "PlayingCardDeck.h"  
//@class PlayingCardDeck;  
@interface PlayingCard :  NSObject  
+ (NSArray*) suitStrings;  
+ (NSArray*) rankStrings;  
+ (NSUInteger) maxRank;  
- (id)initCardWithRank: (NSUInteger) r andSuit: (NSString*) s;  
- (NSString*) description;  
- (NSUInteger) pokerEvalRankWithDeck: (PlayingCardDeck *) deck;  
- (NSAttributedString *) attributedContents;  
- (BOOL) isEqual:(PlayingCard*)object;  
@property (strong, nonatomic) NSString *contents;  
@property (nonatomic, getter = isUsed) BOOL used;  
@property (nonatomic, readonly) NSInteger rank;
@property (nonatomic, readonly, strong) NSString * suit;  
@end

---

//  PlayingCard.m  
#import "PlayingCard.h"  
@interface  PlayingCard()

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Answer 1

That looks like a typical "import cycle":

 // In PlayingCardDeck.h:
 @import "PlayingCard.h"

 // In PlayingCard.h:
 @import "PlayingCardDeck.h"

Replacing one of the @import statements by @class should solve the problem, e.g.

 // In PlayingCardDeck.h:
 @class PlayingCard; // instead of @import "PlayingCard.h"

And in the implementation file you have to import the full interface:

 // In PlayingCardDeck.m:
 #import "PlayingCardDeck.h"  
 #import "PlayingCard.h"    // <-- add this one