Relieved Portsmouth booked their place in the FA Cup quarter-finals after Preston midfielder Darren Carter scored a 93rd-minute own-goal to decide an action-packed fifth-round tie at Deepdale.
North End, fourth bottom in the Coca-Cola Championship, belied their lowly status with a vibrant display and the award of a 60th-minute spot-kick put them on course for a famous victory.
But man-of-the-match David James flung his 6ft 5in frame to his right to deny Preston midfielder Simon Whaley.
James also made a string of fantastic saves - including a wonderful 74th-minute stop to deny substitute Neil Mellor - as Preston piled on the pressure in the second half.
A replay looked certain as the game drifted into the final minute of added time but Niko Kranjcar's corner was missed by Preston goalkeeper Andy Lonergan and in the panic Carter could only smash the ball into his own net from underneath the crossbar.
Hermann Hreidarsson appeared to knock the ball towards goal with his hand as the corner drifted across the six-yard box but referee Mike Dean failed to spot the incident and the goal stood.
In Sunday's other tie Sheffield United narrowly missed out on a third Barclays Premier League scalp in this season's FA Cup and had to settle for a goalless draw against Middlesbrough.
New Sheffield United manager Kevin Blackwell was denied a winning start on his return to Bramall Lane only by the post.
Former Everton striker James Beattie struck the upright just before the break for the Blades - who also had two good penalty appeals for handball waved away - and that was the closest either side came.
In the second half Paddy Kenny produced two saves in the space of 60 seconds to deny Mido and then David Wheater.
Then, at the death, Emanuel Pogatetz's header almost won the game for the visitors but his effort was blocked by Chris Morgan.
After beating Bolton and Manchester City in previous rounds, Blackwell and United still have a chance to progress - and will at least be in the hat for Monday's quarter-final draw.
But if the Coca-Cola Championship side are to reach the sixth round they will have to do it the hard way as they face a replay at the Riverside on February 26.
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