In 1998, he reached the last 48 at the Irish Open, losing 3–5 to Billy Snaddon, but made no further progress in any tournament that season.

The following season, he reached the last 32 at the 2000 Scottish Open, where he defeated Nick Pearce, John Read and Jamie Burnett before losing 3–5 to Mark Williams.

In that year's World Championship, he beat Joe Jogia, John Lardner, Joe Johnson, Rod Lawler and Terry Murphy to set up a meeting in the first round at the Crucible Theatre with Stephen Lee.

Helgason played at the last 32 stage of a ranking event for the third time at the 2002 British Open; there, he defeated Jin Long, Ryan Day, Stuart Bingham, Patrick Wallace and Dave Harold, but lost 3–5 to Paul Hunter.

Having reached a career-high ranking of 66th for the 2003/2004 season, Helgason played in only the first two tournaments, losing in the LG Cup 4–5 to Ian Brumby and in the British Open, 4–5 to Michael Wild.