Based on the results you posted, it doesn't sound like you have full access to the destination directory. Program files can be copied, but the ability to 'overwrite' files does not appear to be there.

To test this out, create and save a document using MS Word or Excel, to the same directory on the network. Close the document and create a new document and attempt to save it as the same file name as the one already there. If you get an error message (apart from the standard warning that the file already exists), then this indicates a network rights scenario.

There may be properties on the drive that don't allow overwriting files (apart from user rights); I have seen this before with Novell. We cannot help you to troubleshoot any particular network settings.

FYI: Opportunistic locking is a workstation setting (actually 3 settings) stored in the Windows registry, and is used for 'file caching' and network speed improvement. However in a multi-user environment (such as accounting applications) this usually results in corrupt data, which is why we detect and turn it off. This is important to do, but not likely the cause of your installation scenario.