VFP treats '&&' as begining of inline comment regardless if it's inside string literal or not. IMO, it's a bug which not going to be be fixed.
You'll have to either split string literal or replace '&' with CHR(38)

UPPER(Password)="&" + "&ETC       " 
* or
UPPER(Password)= CHR(38) + CHR(38) + "ETC       " 

>My SQL was like this:
>
>

>SELECT Numero AS PrimaryKey,Session FROM Member WHERE UPPER(Username)="SOMETHING" AND UPPER(Password)="&&ETC       " ORDER BY 1
>

>
>But, this generates an error in VFP. The cause is the double ampersands. How can I adjust to support such a search in my SQL?