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Gregg Allman's health continues to be an issue. 

Portland's Waterfront Blues Festival spokesman Peter Dammann tells The Oregonian the 66-year-old rocker cancelled his upcoming appearance at this weekend's event along with two other performances, and checked into a hospital.  He adds that Allman's rep didn't give him "any specifics on what's happening with Gregg." 

Allman was supposed to perform at the festival on Sunday.  He also cancelled a show Monday in Boise, Idaho, and a date Wednesday in Woodland Park, Washington. 

Allman's agent isn't shedding any additional light on the situation, only telling The Oregonian that Gregg "has been forced to cancel" his shows this week "due to unforeseen circumstances."  The rep says nothing about Allman being in the hospital. 

Allman, who underwent a liver transplant in 2010, has missed a number of concerts this year for health reasons.  The Allman Brothers Band had to reschedule a number of shows in New York in March when Gregg came down with bronchitis.  In April he had to end his first-ever Australian tour early because of a broken wrist. 

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