[Bugs galore in the 4.0 update for me!]

Same issue for me here, disabling GPU rendering fixed it. Made an account to give you all some diagnostic info. Also, on a side note, isn't 3 layers of spam blocking a bit excessive?

Application	paint.net 4.0 (Final 4.0.5288.36565)
Build Date	Tuesday, June 24, 2014
	
Hardware accelerated rendering (GPU)	True
Animations	True
Language	en-US
	
OS	Windows 8.1 (6.3.9600.0)
.NET Runtime	4.0.30319.34014
Physical Memory	12,175 MB
	
CPU	Intel(R) Core(TM) i7-4700MQ CPU @ 2.40GHz
    Architecture	x64 (64-bit)
    Process Mode	64-bit
    Speed	~2394 MHz
    Cores / Threads	8
    Features	DEP, SSE, SSE2, SSE3, SSSE3, SSE4_1, SSE4_2, XSAVE
	
Video Card	NVIDIA GeForce GTX 770M
    Dedicated Video RAM	2,986 MB
    Dedicated System RAM	0 MB
    Shared System RAM	6,087 MB
    Vendor ID	0x10DE
    Device ID	0x11E0
    Subsystem ID	0x10E81462
    Revision	161
    LUID	0x0000C44C
    Flags	None
    Outputs	1
	
Video Card	NVIDIA GeForce GTX 770M
    Dedicated Video RAM	2,986 MB
    Dedicated System RAM	0 MB
    Shared System RAM	6,087 MB
    Vendor ID	0x10DE
    Device ID	0x11E0
    Subsystem ID	0x10E81462
    Revision	161
    LUID	0x0000C8D0
    Flags	None
    Outputs	0
	
Video Card	Microsoft Basic Render Driver
    Dedicated Video RAM	2,986 MB
    Dedicated System RAM	0 MB
    Shared System RAM	6,087 MB
    Vendor ID	0x1414
    Device ID	0x008C
    Subsystem ID	0x00000000
    Revision	0
    LUID	0x0000C843
    Flags	Software
    Outputs	0