While the Windows Event System/Application logs can be helpful, they are really secondary to the QlikView Server logs. Would suggest that you configure QVS logging to High Verbosity so that as much information as possible will be written to the QVS Events log.
Base upon the errors you reported, it seems there has been some .Shared file corruption. QVS has built-in .Shared file cleaning functionality, so would suggest that you use it. When you do, be sure to make backups of the .Shared file first.
Hope this helps,