functions - Strange ::usage behavior in v9

Bug fixed in 9.0.1

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Something has gone wrong with usage in Mathematica 9. Would someone tell me how to fix it?

I define a function pR with a usage such that there is a line break (see below)

pR::usage = "pR[s,m0,m1] is a function that looks like

    pR(s,m0,m1)=s+m0+m1.";
pR[s_, m0_, m1_] := s + m0 + m1

And then, I subsequently call the defined function the next cell (without running it),

pR[a,b,c]

Then, when I move with the cursor somewhere within the arguments of the pR function, and move it left and right with the arrow keys, I get a bunch of StringMatchQ::strese errors which makes no sense to me.

But if I remove the line-break,

pR::usage = "pR[s,m0,m1] is a function that looks like 
  pR(s,m0,m1)=s+m0+m1.";
pR[s_, m0_, m1_] := s + m0 + m1

and try calling the function and placing my I-beam in the argument, I don't get these strange errors. Can anyone help?

Answer

Unformatting the usage message cell and changing \n\n to \n\\[IndentingNewLine] will cure it.