I used to be able to get ö by pressing and holding the o key.

Question

Maverick version OS X 10.9.4 (13E28)
Up until this morning, 16 Sept, on any word processor (Pages, Word for Mac, PlainText, Notes) I could access European alternatives to each of the vowels of the alphabet by pressing and holding the letter key.
Now all I get is a repeat of the letter.
The question is: how do I return to the pre Sept 16 situation?

Answer 1

Thank you all for your responses.
I am most definitely the non-technical user compared to you guys. I’m never going to be in the position of responding with confidence to anyone requesting help in this forums; you folk may therefore have this information at your finger-tips.
One of the best features of mac os x that I discovered only purchasing the iMac in 2013 was feature that by pressing and holding down a letter key a list of alternative language options appears. This feature disappeared on Sept 16. At the same time the outcomes of pressing and holding a combination of keys (most used Shift + Down Arrow) or a single key also disappeared. The most obvious of the single key outcomes was the continuous movement of the cursor along a line when Left or Right arrow was pressed and held down.
Initially, the replacement outcome was if I pressed and held a letter key I simply got multiple repetitions of the same letter. Not finding my problem in the support forums I posed the initial problem.
While this solved the problems of multiple repetitions it did not solve anything else.
I finally sought help from Apple Support Chat over a 36 hour period.
1st senior supervisor & 1st Solution
2nd senior supervisor confirms 2nd solution (and confirms if 2nd solution does not work there is a 3rd solution).
These two senior supervisors were intrigued by the problem and both shared the same view of problem and the same solution.
PROBLEM - there is no location within Mavericks OS X that enables anyone to either switch-on or switch-off the outcomes of pressing and holding a key or a combination of keys. Consequently there is no easy quick fix.
Since neither senior supervisor had, previously, been faced with this particular problem they could only project ideas for causes, software incompatibility or a serious hardware problem, which could only be fully resolved by returning my iMac to Apple ReSeller (3rd solution). Having no desire to entrust my iMac to the slightly dubious Estonian postal service, doing this would require two return journeys (taking and collecting 10 days later) involving 4x6 hours of motorway driving plus a 4x3 hour ferry and costs in excess of €350.
SOLUTION - 3 were suggested to be tried in sequence if the first did not work. Reinstall Mavericks using instructions found at http://support.apple.com/kb/ph13871; (ii) Erase and Install Mavericks using instructions found at http://support.apple.com/kb/PH14243 and (iii) return to Reseller.
As had no effect, I attempted (ii) which involved a lot of hassle, but has returned all the functions of the keys.
The downside is that I still don’t know what caused the problem. The only app I downloaded to the iMac on the September 15th was a Garmin Fitness app. “Once bitten twice shy” I shall download the Garmin Fitness app to my Airbook and will keep you folks informed…….