The curator of Ronnie DeSillers' estate has sued a savings and loan to recover nearly $200,000 she claims the thrift allowed to be improperly withdrawn by the boy's mother. Court-appointed curator Karen Gievers on Tuesday filed suit in Dade Circuit Court against Coral Gables Federal Savings & Loan for allowing Maria DeSillers to withdraw and spend the money, which was donated to pay for Ronnie's medical bills and to help other young liver transplant patients. The withdrawal, she argued, was contrary to state law. The thrift knew the purpose of the money, Ms. Gievers alleged. Seven-year-old Ronnie died at Pittsburgh Children's Hospital in April 1987 while awaiting a fourth liver transplant, and his mother has been involved in legal disputes ever since for refusing to pay the balance of the boy's medical bills. She claims her son received improper care, which the hospital denies. DeSillers is accused of withdrawing about $260,000 from the Coral Gables Federal account, but less than $60,000 has been recovered. The money was allegedly spent on a used BMW car and jewelry, and some was given to her ex-husband and her boyfriend. Some $690,000 were donated to Ronnie from around the country, including $1,000 from President Reagan and $200,000 from Miami Beach industrialist Victor Posner, after a small fund collected by his school was repored stolen. Meanwhile, DeSillers' boyfriend and former fiance, Jose Castillo, pleaded innocent Tuesday to charges that he pawned stolen computer equipment. Castillo, who is free on bond, is charged with third-degree grand theft for possession of the stolen computer and with unlawful consignment of property to a pawn shop. DeSillers accompanied Castillo to the Broward County pawn shop April 2. Circuit Judge Mel Grossman scheduled trial for Nov. 7.