has anybody ever had this problem & what can b done to resolve it. sometimes the flash (new 5600hs, & 5200i?) doesn't flash even when the batteries r new. doesn't matter whether i'm using my 9xi or 7000i. this happens maybe 2-4x per roll. this is a potential problem if i'm shooting a wedding, etc. for a customer. other than that, my photos turn out great w/ perfect exposure. would appreciate any suggestions. thanx.