FoxPro DBF Index Corruption

We are running a pretty popular application in Russia and other CIS countries through a pretty old accounting system called BEST. It's all built on FoxPro (not Visual Foxpro) DBF/CDX tables. It's open but it doesn't have API for interacting with other software. So we have to use direct access to the tables and data. We use Sybase Advantage Database Server (ADS Internet Connector) to connect our online store to BEST. During developing, testing and running it for the first three months everything was fine. But almost half year ago we started to get index corruption errors. We tried almost everything - replaced network cables and NICs, RAID controller with HDDs, memory, reinstalled windows server. We rebuilt the tables and indexes, looked into the logs - but everything is useless. Once in two days we get index corruption error, so we have to stop the server, reindex tables and start it again and the whole company is waiting for 10 minutes. We have problems with only 2 tables - orders and their contents. All other 300 tables that are used are never harmed. One more problem that is making the case harder is that the problem is not immediate. When the index file is broken - it's not seen. Users continue to work, until one of them starts a new session BEST or a client makes an order. So it's impossible to catch the moment when it happenes. Right now we are blaming ADS. Does anyone know about such problems and their solutions in ADS. I've surfed all the internet looking for answers, but found none. Thanks, if you know something.