This is occurring on 2 new Windows XP Pro Workstations in a peer to peer environment trying to use either local shares on the local workstation (ie mapping C:\sharedfolder to S. Google search for the issue finds a MS knowledge base article regarding adding IRPStackSize and a value of 15 or more, also indications are it's connected to a 2011 event log error and known to occur if using NAV. These machines have never had any AV installed but NOD32. After making the IRPStackSize change (leaving NOD32 installed) and rebooting the problem doesn't go away. After removing the IRPSTackSize key and uninstalling NOD32 the problem goes away immediately. So, what's the deal (meaning the reason this should be happening at all) and is there a fix (that doesn't require jumping through hoops)? It seems to me that neither NOD32, or any other AV product for that matter, should be getting in the way of any network shares for any reason. (Good a product as it may be otherwise). Frankly, it's this sort of intrusiveness that has caused us to stop using and/or recommending NAV, etc. (we're system specifiers) This shouldn't be this difficult to deploy. cef1000 An update on this issue for those interested or experiencing this problem: 1. An FYI, these are brand new workstations, newly activated, fully patched and after base productivity apps were installed, NOD 32 was installed, for purposes of testing there is NO 3d party Firewall installed and the MS Firewall is disabled. 2. Problem goes away if NOD32 is un-installed 3. After uninstalling NOD32 installed the demo of Kaspersky and it has the same problem. 4. I'm done trying AV products to see if it involves all of them. Best educated guess: Initial Conclusion (And apologies to NOD32 for my frustration and impatience). This may have something to do with MS Patches, likely the very recent ones. If so, it may be affecting every Anti Virus vender's product. There is a MS KB article about an event log Id 2011 and this error message, but, the "fix" doesn't work in this situation and one KB article points to NAV, but, also involves ram issues. Latest update: Though Kaspersky does this, Panda does not have this problem.