XCode internal error

While working on XCode I am continuously facing this error:

Internal Error

Uncaught Exception:
*** -[DTMutableRangeArray rangeAtIndex:]: index (1) beyond bounds (0).

Stack Backtrace:
The stack backtrace has been logged to the console

With two options: Quit/ Continue

This happens when I perform simple editing on Xcode !

The message obtained in console is:

6/16/09 12:19:05 PM Xcode[121] ** INTERNAL ERROR: Uncaught Exception **
Exception: *** -[DTMutableRangeArray rangeAtIndex:]: index (1) beyond bounds (0).
Stack:
0 0x905d20ab __raiseError (in CoreFoundation)
1 0x90b4de3b objc_exception_throw (in libobjc.A.dylib)
2 0x905d1e8b +[NSException raise:format:arguments:] (in CoreFoundation)
3 0x905d1eca +[NSException raise:format:] (in CoreFoundation)
4 0x0005e70c _DTRangeArrayRaiseBoundsException (in DevToolsFoundation)
5 0x0005ef8a -[DTMutableRangeArray rangeAtIndex:] (in DevToolsFoundation)
6 0x00254387 -[XCTextView _displayAutoHighlightTokens] (in XcodeEdit)
7 0x00255496 -[XCTextView _autoHighlightTokenWithTimer:] (in XcodeEdit)
8 0x90658493 __NSFireTimer (in Foundation)
9 0x90558ac5 CFRunLoopRunSpecific (in CoreFoundation)
10 0x90558c78 CFRunLoopRunInMode (in CoreFoundation)
11 0x96e8828c RunCurrentEventLoopInMode (in HIToolbox)
12 0x96e880a5 ReceiveNextEventCommon (in HIToolbox)
13 0x96e87f19 BlockUntilNextEventMatchingListInMode (in HIToolbox)
14 0x950f2d0d _DPSNextEvent (in AppKit)
15 0x950f25c0 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] (in AppKit)
16 0x950eb5fb -[NSApplication run] (in AppKit)
17 0x950b8834 NSApplicationMain (in AppKit)
18 0x00002bca

Does anyone know why is it occurring and how can I resolve it

Thanks, ... in advance!