I'm unable to play an episode of podcast in iTunes in Full HD

I could do so two weeks ago but can't now. I was trying to watch an old Apple keynote and it stalled.

Console displays this sort of messages repeatedly on every stall:

26.03.15 2:27:26,000 kernel: Limiting closed port RST response from 314 to 250 packets per second
26.03.15 2:33:32,914 Dock: kCGErrorIllegalArgument: CGSSetWindowListGlobalClipShape: Invalid window 0x46f
26.03.15 2:33:32,914 Dock: kCGErrorIllegalArgument: CGSSetWindowListGlobalClipShape: Invalid window 0x46f
26.03.15 2:33:32,914 Dock: kCGErrorIllegalArgument: CGSSetWindowListGlobalClipShape: Invalid window 0x46f
26.03.15 2:33:32,915 Dock: kCGErrorIllegalArgument: CGSSetWindowTransformsAtPlacement: Failed
26.03.15 2:33:32,915 Dock: kCGErrorIllegalArgument: CGSSetWindowTransformAtPlacement: Failed
26.03.15 2:33:32,915 Dock: kCGErrorIllegalArgument: CGSSetWindowTransformAtPlacement: Failed
26.03.15 2:33:32,931 Dock: kCGErrorIllegalArgument: CGSSetWindowListGlobalClipShape: Invalid window 0x46f
26.03.15 2:33:32,931 Dock: kCGErrorIllegalArgument: CGSSetWindowListGlobalClipShape: Invalid window 0x46f
26.03.15 2:33:32,931 Dock: kCGErrorIllegalArgument: CGSSetWindowListGlobalClipShape: Invalid window 0x46f
26.03.15 2:33:32,931 Dock: kCGErrorIllegalArgument: CGSSetWindowTransformsAtPlacement: Failed
26.03.15 2:33:32,931 Dock: kCGErrorIllegalArgument: CGSSetWindowTransformAtPlacement: Failed
26.03.15 2:33:32,932 Dock: kCGErrorIllegalArgument: CGSSetWindowTransformAtPlacement: Failed
26.03.15 2:33:32,932 Dock: kCGErrorIllegalArgument: CGSOrderWindowListWithOperation
26.03.15 2:33:32,932 Dock: kCGErrorIllegalArgument: CGSOrderWindowList

In Activity Monitor I see the following figures:

Swap - 128.3 MB, Pages In - 746 MB, Pages out - 162 MB.

iTunes 10.6.3