Daniel Radcliffe was stopped by US guards while crossing over the border from Canada to the US because he failed to upgrade his visa.
The 'Harry Potter' star had been in Toronto to attend the premiere of 'What If' with co-star Zoe Karan plus to celebrate his 25th birthday and he was also in the process of upgrading his P-2 visa, for foreign actors and entertainers, to an O-1 visa for the individual who possesses extraordinary ability in the sciences, arts, education, business or athletics, the Daily Express reported.
An O-1 grants the holder a three-year stay in the US, while the P-2 only gives a performer residency for the time they would be working on a project, not to exceed a year.
Radcliffe was on his way to attend Comic-Con in San Diego to promote another darker film 'Horns'.
A spokesman told the New York Post that Radcliffe had been approved for the upgrade but needed a stamp from the US embassy in Toronto and their computer was down, which caused the problem.
The 25-year-old actor did eventually get to San Diego, just in time to appear on a Comic-Con panel with Horns co-star Juno Temple and director Alexandre Aja.