Examples of mathematicians who lost interest in Math and got interested again? I am looking for some examples, and hopefully some short biographies on mathematicians who lost interest in Math along the way, and somehow got rejuvenated again. (Better still, who managed to do something interesting)
I hope to gather these examples to encourage myself. Any help would be very much appreciated. Thanks!
 A: I think the most famous example would be Blaise Pascal, who put his scientific interests to the side in 1654 to focus on religous matters. Fortunately (for us), in 1658 he had a bad toothache, and one sleepless night he started thinking about the cycloid to divert his thoughts. The rest is history.... 
A: Someone who lost interest in math, regained interest in math, then lost interest in it again.
Also according to this article Newton lost interest in math and physics quite often.
A: Andy Vázsonyi was a childhood friend of Paul Erdős, with whom he shared a doctoral advisor (L. Fejér) and coauthored a couple of early papers.
However Vázsonyi took an interest in applied mathematics, becoming a leader in operations research.  Among the several stories he wrote about Erdős after his death is a terse account, later elaborated in the afterword to the book Erdős on Graphs, of a return to pure mathematics.  He wrote:

According to Erdős a mathematician who stopped doing math was dead: he
  died a most ignominious death. I was a victim of World War II so Erdős
  forgave me. “Those were difficult times,” he said. But in 1960 I
  proved a very difficult theorem in geometry and Erdős told Laura [Andy's wife],
  “Strange, Vazsonyi is dead, but never lost the touch. Yesterday he
  found a proof straight from the Big Book.”

A: It's not 100% clear that Grothendieck lost interest in mathematics, but it seems that he didn't make any mathematical research during almost the whole 1970's.
He began to release mathematical research papers in early 1980's.
From Wikipedia:

After leaving the IHÉS, Grothendieck became a temporary professor at Collège de France for two years. A permanent position became open at the end of his tenure, but the application Grothendieck submitted made it clear that he had no plans to continue his mathematical research. The position was given to Jacques Tits.
He then went to Université de Montpellier, where he became increasingly estranged from the mathematical community. Around this time, he founded a group called Survivre, which was dedicated to antimilitary and ecological issues. His mathematical career, for the most part, ended when he left the IHÉS.

