how about this...
{=IF(SUM(--(Sheet1!A1:Z1=Sheet2!A1:Z1)) < COUNTA(Sheet1!A1:Z1)+COUNTBLANK(Sheet1!A1:Z1),"PROBLEM","OK")}
<?XML:NAMESPACE PREFIX = COUNTA(Sheet1!A1 /><COUNTA(Sheet1!A1:Z1)+COUNTBLANK(Sheet1!A1:Z1),"PROBLEM","OK")}< p>
again an ARRAY confirmed with CTRL > SHIFT > ENTER
let me know
</COUNTA(Sheet1!A1:Z1)+COUNTBLANK(Sheet1!A1:Z1),"PROBLEM","OK")}<>