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Twitter Inc., the social-networking service that lets users share 140-character messages, said it’s looking into an increase in error rates that’s making it harder to access the site.

“We are aware of the problem and taking action,” the San Francisco-based company said today at about 3 p.m. New York time on a blog devoted to the site’s status.

Twitter has struggled with service disruptions as its traffic surges. The average number of postings sent daily rose to about 140 million in the past month, up from 50 million a year earlier, the company said this week. Twitter had reported “elevated error rates” an additional four times in February, along with a range of other difficulties.

The company is increasingly counting on its site to deliver advertising, potentially putting more revenue at stake when the service goes down. Twitter’s surging prospects and potential ad revenue have helped drive up its valuation. It was valued at $3.7 billion in December when it received an investment led by venture-capital firm Kleiner Perkins Caufield & Byers. That compares with $1 billion in September 2009, according to a person familiar with the matter.

(Source: Bloomberg)