Index: Chat Core/MVIRCChatConnection.h
===================================================================
--- Chat Core/MVIRCChatConnection.h	(revision 4401)
+++ Chat Core/MVIRCChatConnection.h	(working copy)
@@ -32,6 +32,9 @@
 	BOOL _watchCommandSupported;
 	BOOL _sendQueueProcessing;
 	BOOL _pendingIdentificationAttempt;
+	NSString *_failedNickname;
+	NSInteger _failedNicknameCount;
+	BOOL _nicknameShortened;
 }
 + (NSArray *) defaultServerPorts;
 @end
Index: Chat Core/MVIRCChatConnection.m
===================================================================
--- Chat Core/MVIRCChatConnection.m	(revision 4401)
+++ Chat Core/MVIRCChatConnection.m	(working copy)
@@ -623,6 +623,10 @@
 	if( ! [_chatConnection connectToHost:server onPort:serverPort error:NULL] )
 		[self performSelectorOnMainThread:@selector( _didNotConnect ) withObject:nil waitUntilDone:NO];
 	else [self _resetSendQueueInterval];
+
+	_failedNickname = nil;
+	_failedNicknameCount = 0;
+	_nicknameShortened = NO;
 }

 - (oneway void) _ircRunloop {
@@ -673,6 +677,10 @@
 		[self scheduleReconnectAttempt];
 	}

+	[_failedNickname release];
+	_failedNicknameCount = 0;
+	_nicknameShortened = NO;
+
 	[super _didDisconnect];
 }

@@ -2120,10 +2128,20 @@
 		NSString *nick = [self nextAlternateNickname];
 		if( ! [nick length] && [parameters count] >= 2 ) {
 			NSString *lastNickTried = [self _stringFromPossibleData:[parameters objectAtIndex:1]];
-			nick = [lastNickTried stringByAppendingString:@"_"];
+
+			if( ( _failedNickname && [_failedNickname isCaseInsensitiveEqualToString:lastNickTried] ) || _nicknameShortened) {
+				nick = [[lastNickTried substringToIndex:([lastNickTried length] - 2)] stringByAppendingString:[NSString stringWithFormat:@"_%d", _failedNicknameCount]];
+
+				_nicknameShortened = YES;
+			} else nick = [lastNickTried stringByAppendingString:@"_"];
 		}
+
+		if ( ! _failedNickname ) _failedNickname = [[self _stringFromPossibleData:[parameters objectAtIndex:1]] copy];

 		if( [nick length] ) [self setNickname:nick];
+
+		if ( _failedNicknameCount < 9 ) _failedNicknameCount++;
+		else _failedNicknameCount = 0;
 	} else {
 		// "<current nickname> <new nickname> :Cannot change nick"
 		// - Sent to a user who is changing their nickname to a nickname someone else is actively using.