UPDATE 5/6/14 11.25am: Ubisoft has told Eurogamer that the bug blocking some users from booting Watch Dogs is not related to uPlay rewards.
"The Watch Dogs team is aware of this problem and is working to find a fix for the players it affects," a Ubisoft spokesperson said. "The issue is not specifically related to Uplay Rewards, and we're doing our best to find a solution.
"In the meantime, players can submit a ticket at support.ubi.com if they are encountering this issue."
Ubisoft hasn't said what is causing the problem, but users shouldn't worry about downloading any of the game's uPlay rewards.
ORIGINAL STORY 4/6/14 11.15am: A number of Watch Dogs owners have been left unable to load the game due to a bug with the title's uPlay rewards, reports suggest.
In an enormous 197-page thread on Ubisoft's official forum, countless users have said that they can't play the game after redeeming uPlay content on PC, PlayStation 3, PlayStation 4, Xbox 360 and Xbox One. But others, meanwhile, have downloaded the content and remained unaffected.
A number of extras are available to those who interact with the uPlay app or via uPlay.com.
For example, you can unlock a gold-coloured D50 gun and the Papavero Stealth Edition car that helps you evade detection, as well as cash bonus reward and a uPlay avatar. It's the first two of these that are apparently causing problems.
When booting a save, the progress bar will get to around 90 per cent and then refuse to move further, meaning users are left at the game's title screen.
Ubisoft has said it is aware of the issue and is now "isolating" the problem.
"We're aware some of you are stuck on the loading screen," read a message posted to the official Watch Dogs Twitter account last night. "We're hard at work on isolating the problem to find a fix."
"If you're encountering that issue, please submit a ticket to http://support.ubi.com to help move forward. Thanks for understanding."
Regardless of the issue, Watch Dogs is generally off to a stellar start. Over 4m copies have now been sold, making it the biggest game launch in Ubisoft's history and the best new launch for a game IP ever in the US and UK.
We’re aware some of you are stuck on the loading screen. We’re hard at work on isolating the problem to find a fix. (1/2)— Watch Dogs (@watchdogsgame) June 3, 2014
If you’re encountering that issue, please submit a ticket to http://t.co/HXXJuATnWk to help move forward. Thanks for understanding. (2/2)— Watch Dogs (@watchdogsgame) June 3, 2014