Articles running in this week's tabloids claim Witherspoon decided to end her marriage to the Crash star, 32, after learning he had romanced Cornish on the set of their new movie, Stop Loss, in Texas.
The reports go so far as to suggest that the Legally Blonde star, 30, found out about her husband's alleged romance with Cornish after reading a saucy note on his BlackBerry phone.
But Cornish, 24, insists the reports are all false.
In a statement, released yesterday, her publicist writes, "It's not true. They are costars and that is it."
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