I recently updated the local antivirus on my SharePoint 2010 server and noticed users were getting "access denied" errors when trying to upload documents. Turns out I had forgotten to update the folders my antivirus solution should ignore.
A quick search turned up this: http://support.microsoft.com/kb/952167
Basically go to the drive you installed SharePoint 2010 on (D: drive in my case) and exclude the following:
Drive:\Program Files\Microsoft Office Servers\14.0\Data
Drive:\Program Files\Microsoft Office Servers\14.0\Logs
Drive:\Program Files\Microsoft Office Servers\14.0\Bin
The above folders handle indexing for your farm.