SOLVED
I had foolishly assigned a macro to the Ctrl-Shift-S key combination in AutoHotKey.
Boy, do I feel dumb.
For some reason, the documented keyboard shortcut for 'Save As...', Ctrl-Shift-S, doesn't work for me. When I press that key combination, several items on the toolbar flash as they're accessed and the tool changes to the Text tool. Is there a way to restore the proper shortcut function? I have the latest update. I'm wondering if it's in one of the add-ons? I'm including diagnostics in case that's helpful.
Thanks for any assistance anyone can provide.
Application paint.net 4.0.13 (Final 4.13.6191.1824)
Build Date Tuesday, December 13, 2016
Hardware accelerated rendering (GPU) True
Animations True
DPI 96.00 (1.00x scale)
Language en-US
OS Windows 8.1 (6.3.9600.0)
.NET Runtime 4.0.30319.42000
Physical Memory 8,084 MB
CPU Intel(R) Core(TM) i3-3130M CPU @ 2.60GHz
Architecture x64 (64-bit)
Process Mode 64-bit
Speed ~2594 MHz
Cores / Threads 2 / 4
Features DEP, SSE, SSE2, SSE3, SSSE3, SSE4_1, SSE4_2, XSAVE
Video Card Intel(R) HD Graphics 4000
Dedicated Video RAM 32 MB
Dedicated System RAM 0 MB
Shared System RAM 1,760 MB
Vendor ID 0x8086
Device ID 0x0166
Subsystem ID 0x1971103C
Revision 9
LUID 0x000092D5
Flags None
Outputs 1
Video Card Microsoft Basic Render Driver
Dedicated Video RAM 0 MB
Dedicated System RAM 0 MB
Shared System RAM 256 MB
Vendor ID 0x1414
Device ID 0x008C
Subsystem ID 0x00000000
Revision 0
LUID 0x00009468
Flags Software
Outputs 0