It's not just office workers suffering from the blues as they shuffle back to work - a number of technology giants have been hit by post-Christmas woes too.
Google's Gmail was blocked in China after months of disruptions to the world's biggest e-mail service, with an anti-censorship advocate suggesting the Great Firewall was to blame.
Large numbers of Gmail Web addresses were cut off in China on Friday, said GreatFire.org, a China-based freedom of speech advocacy group. Users said the service was still down yesterday.
"I think the government is just trying to further eliminate Google's presence in China and even weaken its market overseas," said a member of GreatFire.org, who uses a pseudonym. "Imagine if Gmail users might not get through to Chinese clients. Many people outside China might be forced to switch away from Gmail."
A Singapore-based spokesman for Google said in an e-mail: "We've checked and there's nothing wrong on our end."
Almost all of Google's services have been heavily disrupted in China since June, but up till last week Gmail users could still access e-mail downloaded via protocols like IMAP, SMTP and POP3. These had let people communicate using Gmail on apps like the Apple iPhone's Mail and Microsoft Outlook.
Chinese Foreign Ministry spokesman Hua Chunying said she did not know anything about Gmail being blocked, adding that the government was committed to providing a good business environment for foreign investors.
"China has consistently had a welcoming and supportive attitude towards foreign investors doing legitimate business here," she said. "We will, as always, provide an open, transparent and good environment for foreign companies in China."
Meanwhile, Twitter on Sunday experienced a partial outage, the nature of which was not immediately clear, the company said.
"Something is technically wrong," the microblogging service's welcome page said. "Thanks for noticing - we're going to fix it up and have things back to normal soon."
Users reported problems on the Twitter application for Android and iPhone smartphones, while tweets on the computer application TweetDeck were showing up as having been posted a year ago.
Connection problems also continued to plague Sony's PlayStation Network for a fourth straight day since hackers attacked the video game network, and the company said on Sunday that service was gradually being restored.
The hacker activist group known as Lizard Squad has claimed responsibility for disrupting both the PlayStation Network and Microsoft's Xbox Live on Christmas Day. Service was restored to Xbox Live on Friday.
Some gamers said on Twitter that they were able to access the PlayStation Network on Sunday, but others complained about the continuing outage.
On Sony's Twitter customer support account, AskPlayStation, a representative wrote: "Network services are gradually coming back online."
Late last month, Sony Pictures' computer system was taken down by hackers protesting against the film The Interview, which depicts the assassination of North Korean leader Kim Jong Un. United States President Barack Obama has blamed the North Korean government for the attack.