We set an initial password and force a change. All stored in AD. Pupils can change their own, and staff have access to a cut and locked down mmc console to change student passwords. Saves a lot of minor jobs.
We have seen this where there is a conflict between drivers. Try making a selection profile that only uses one set of network drivers to try to pinpoint the erroneous driver.
You could set up WebDAV on your server and allow the iPads to use WebDAV navigator or other such app. This allows browsing of windows shares via iPad as long as nfts permission allows access.