Pretty self-explanatory. This is what I'm getting in build mode:


I am unable to use any of the clickable, visible icons when this happens.
I can press F5 on my keyboard (Options), go to Edit Town mode, and return to the lot with the build bar reappearing... but only for a short while.
This is the only solution I have found, albeit temporary.

This doesn't happen in live mode (during gameplay).
Does anyone know what causes this or a way to fix it?

I've had this happen a grand total of twice since purchasing IP on release day -- the first time was after I spent several hours building a lot and thought that I had no way to save it. Managed to enter Edit Town mode and saved the game, so I knew it was more of a "glitch" than a serious issue. I can't remember if I retreated to the Main Menu and then re-entered my world, or if I exited right out of the game and restarted, but it was corrected when I returned.

Oh shnikey, Shoveler.
I, too, was able to save when returning from Edit Town. I named the 1st save "mess," figuring it would be corrupt in some way.
I was able to load the "mess" save, but this problem is ongoing for me whenever I'm building. Hence the help post.
It doesn't matter if I'm building for a short duration of time vs. long builds, Sunset Valley vs. Isla Paradiso, etc.
Maybe I shoulda had a V8 instead of a 1.55.4

• Sims 3 - Invisible Sims and/or User Interface Issues
  If you are experiencing issues with Missing Sim(s) and / or User Interface Issues see the Game Help:UI and Sim Issues^wiki Guide,
  If this doesn't resolve the issue, please answer the questionnaire and be as comprehensive as you can.
  
  

Thanks for the link, HL.
I did check there 1st, but thought it was different than my situation.

Since it's still occurring, I'll go through the questionnaire & post appropriately.
I've added Debug Enabler to my Mods to see if that helps (re. #13 on the questionnaire).
Fingers crossed!

ETA:
1. Which game(s) do you have? Sims 3 [WA, AMB, LN, OLS, GEN, PETS, SUP, SEAS, IP]
2. What is the game version/patch level for the base game? 1.55.4
3. How many sims are missing/invisible? 0
4. Do they have an icon or not? yes
5. Do you have any UI issues? yes - The disappearing half UI issue only occurs in Buy/Build mode. It does not occur in gameplay nor CAS.
6. Were the sims traveling? no
7. How many traveling? 0
8. How are all travellers related? N/A
9. Which country are the sims in? Sunset Valley
10. How many days? N/A
11. Did the sim(s) return via the phone prematurely or only when the vacation was over? N/A
12. Returning together or separate? N/A
13. Are you using Twallan's MasterController+Overwatch+DebugEnabler or AwesomeMod? NRaas' MC & Overwatch
If you're not, you should. And then do the steps in the Already Have the Issue? section above.
Already running MC & Overwatch, but added Debug Enabler. Receiving "color picker" errors via Debug Enabler.
14. Are you using EA Story Progression, Twallan's Story Progression, or Awesome Story? EA's
If you're still using EA's Story Progression, that is buggy, use a mod. Several selections in the Content List.
EA Story Progression. No problem with UI in gameplay.
15. When did the issue start? since 1.55.4 patch
16. What were your sims doing? N/A - UI disappears in buy/build mode only.
17. What things have you tried? removing Mods folder, turning off EA Story Progression
18. What worked? F5 to Options > Edit Town > Return to Game (temporary fix, does not always work)
19. What didn't work? adding NRaas Debug Enabler (see #13)
20. Anything else you would like to add? Right half of UI disappears in Buy/Build mode only and only on larger lots (40x40 and up). None of the clickable icons work. Fairly certain this is relevant to onboard graphics.

I will add that I have not had a graphics card installed since updating to patch 1.55.4 & installing IP. Though all worked well running the game with and without a graphics card prior to patch & IP, I'm certain that it just can't keep up without one anymore. I am replacing my graphics card and will update. Hopefully with a sheepish a-ha.



ETA 11/10/2013:
A graphics card did not make a difference. The UI continues to occasionally disappear in build/buy mode only.

https://leealeesims3.wordpress.com/...-buildbuy-mode/

I found this a year ago and it's saved my ass. But trying to find it again on Google took forever. It's really buried.