>We have a customer who got a new server. Since then they have started to get locking errors about every 2 weeks. We lock a file, update it and then unlock it, but for some reason it gets stuck or the lock doesn't take place. We have dozens of other customers using the same program with no issue. Has anyone any pointers?

First, check the System and Application Event Logs on the workstation(s) and server to see if there are any networking-related warnings or errors. For example, I've seen cases where an old server used a 100Mbit network card, and was replaced with a new server with a 1Gbit card, but the network patch cable could not support the higher speed so errors would crop up. The solution in that case was to replace it with a new Cat 5e or Cat 6 cable.

If the old server was Server 2003 or earlier, and the new one is Server 2008 or later then workstations running Windows Vista or later will talk to it using SMB2 or later. VFP and other so-called "file server" databases work fine with SMB1 as implemented in XP/2003 and earlier but there are known problems with SMB2 and higher.

Some Windows Registry settings can be adjusted to make VFP databases work more reliably on SMB2, see Message#1599945 .