Re-using RSA1 keys as RSA

[Frank Cusack <fcusack%fcusack.com@localhost>]

Is there a security issue with turning an RSA1 key into an RSA key?  One
might want to do this, e.g., to move to protocol 2 without having to
update authorized_keys files.

I thought there was a problem with this, but Google doesn't find anything.

thanks
/fc