Four annoying computer pop-ups you might come across:
17-Across. "You're living in the past," nowadays : UPGRADE REQUIRED.
26-Across. "You can't go there," nowadays : ACCESS DENIED.
45-Across. "Nobody can go there," nowadays : PAGE NOT FOUND.
59-Across. "Never heard of you," nowadays : INVALID USERNAME.
I'm not sure how this ended up on a Thursday, since it seemed very Monday-friendly. Simple, straight-forward theme, without much dreck in the fill. Maybe some of the names could trip up a Monday level solver, but the perps all quickly came to the rescue for me.
Across
1. Explosive sound : BLAM. Boom?! (The perps said "no.")
5. Outer __ : SPACE. And a cross-referential clue at 7-Down. Prefix with 5-Across : AERO.
10. Not even ajar : SHUT.
14. "Born to Die" singer/songwriter Del Rey : LANA. See? All perps!
15. Stadium divisions : TIERS.
16. Son of Leah : LEVI. No perps needed.
20. Flower celebrated in an annual Ottawa festival : TULIP. It all started with a gift of TULIPs by the Dutch Royal Family to the people of Canada after the liberation of Europe in WWII.
21. Move the boat, in a way : ROW. I suppose you could also pedal it?
22. Painting option : SPRAY. Brush? Color? Latex?
23. Like a typical farmer's market : OPEN AIR.
25. "Gotcha!" : OHO.
32. Peace Nobelist Sakharov : ANDREI. Ironically, he was key in the development of the hydrogen bomb, and later played a role in the Partial Test Ban Treaty.
35. Elijah Blue's mom : CHER. With her second husband Greg Allman.
36. __ de coeur: impassioned plea : CRI. Literally, "Cry from the heart" in French.
37. "Gone With the Wind" setting : TARA.
38. "Whew!" : BOY!
39. Sit a spell : REST.
40. The Pac-12's Beavers : OSU. Oregon State University.
41. Ego : SELF.
43. Citrine or amethyst : QUARTZ. Amethyst is the February birthstone. Citrine is November.
48. A Bobbsey twin : NAN. Bert's twin. I wonder if she likes Indian flatbread?
49. Stops : DESISTS.
53. Early New Zealand settler : MAORI.
56. "Something __, something ..." : OLD. "Something old, something new, something borrowed, something blue, and a lucky sixpence in your shoe." I wonder if brides still follow this old advice for a happy marriage on their wedding days.
58. Bug : EAT AT.
62. Cinch : SNAP.
63. Sci-fi staple : ROBOT.
64. Golf shot : CHIP.
65. Breton, e.g. : CELT.
66. Band tour stop, perhaps : ARENA.
67. Building additions : ELLS.
Down
1. Olive Oyl pursuer : BLUTO. D'ah! I tried to cram "Brutus" in there.
2. Eagerly consume : LAP UP.
3. One with degrees? : ANGLE. This was acute clue.
4. Sauce of southern Italy : MARINARA. Mmmm...
5. Norm: Abbr. : STD. Standard.
6. Capital ENE of Custer : PIERRE. WAG.
7. Prefix with 5-Across : AERO.
8. Intercollegiate sport : CREW. They row, row, row their boats.
9. Lawyer's letters : ESQ.
10. Moccasin, for one : SLIP-ON.
11. Man around the Haus : HERR. German.
12. Layer in the eye : UVEA.
13. Considerable : TIDY. As in "A TIDY sum."
18. Posthaste : APACE.
19. Escort : USHER.
24. "Here," on Metro maps : ICI. Nit: the Paris subway is called the Métro, with an acute accent.
25. "__ to Billie Joe" : ODE.
27. Act the cynic : SCOFF. "Scorn" fits, too. Just sayin'...
28. Coming up short : SHY.
29. Bakery specialist : ICER.
30. Before, to a bard : ERST.
31. Scatterbrain : DITZ. I use that word all the time, usually describing myself.
32. On the highest point of : ATOP.
33. Apollo's creator : NASA. No hint of abbr. because it is Thursday?
34. Pharmacopeia listing : DRUG.
38. Abbreviation on a lunch menu : BLT. Oh, so now we get the abbreviation hint!
39. Splendor : RADIANCE. Somehow "Radiance in the Grass" just doesn't have the same ring to it.
41. Gastropod for a gourmet : SNAIL.
42. Geochronological span : EON.
43. "¿__ pasa?" : QUE. "'s up?"
44. Three-time Indy winner Bobby : UNSER.
46. Transported : ENRAPT.
47. Favored to win : ODDS ON. E.g., a bet of "2 to 1 on" means that the team is twice as likely to win as not.
50. "60 Minutes" regular : STAHL. Leslie. I really admire her.
51. Sri Lankan language : TAMIL.
52. What a pedometer counts : STEPS. I bought DH a FitBit for Christmas, thinking it would encourage him to exercise more. The first day he wore it, he announced that he had done almost two miles by just doing his usual stuff around the house. (I was humbled...)
53. Catchall file abbr. : MISC.
54. Archer of "Fatal Attraction" : ANNE. I had forgotten about her role as Michael Douglas's wife.
55. Common face shape : OVAL. ANNE's is a beautiful OVAL, don't you think?
56. Redolence : ODOR.
57. Jiffy __ : LUBE.
60. "Science Friday" radio host Flatow : IRA. He used to be on NPR, but moved to PRI (Public Radio International), which now airs the show.
61. Greek "H" : ETA. Or, Greek "n"?
It's omega for me!
Marti