Just some random thoughts:

Have you checked any logs, etc. to see if your site is under attack (rival colleges)?

Also I noticed lots of traffic when the PCI Compliance people from the credit card company are periodically checking a site.

Had the app pool recycled when things get better?

Is the first (invalid viewstate) near any other errors at the same time? If yes, the other errors may point to a cause. If not, then my guess are: 1) your site is on a cluster of servers and you need to add a machine key to the web.config, or 2) you have moved your viewstate to the bottom of the page and some people are clicking on something that causes a postback before the viewstate finishes loading.

The second error means that the postback (like add to cart) included a non-numeric value in a field that should have had a number. Blanks count as non-numeric, so for example, if the quantity field is blank, you will see this error. Normally the BV pages will prevent posting invalid values. So I suspect either: 1) you have modified a page in a way that allows a real human to post invalid values, or 2) a hacker is trying to break (into) your store, or 3) a non-human client such as HackerScan is posting invalid stuff on purpose to "check the locks".
If there are a lot of the second error at almost the same time and they come in bursts, then it is almost certainly a scan. The load from some scanners can have a negative impact on performance. You may be able to verify the source of the errors by looking at the IIS logs from the same day and time as the errors in the BV log.

I believe that's related to HTML or invalid characters being entered into a form field (Search Box, QTY, etc.).

I did turn off ScanAlert for 3 days to see if that was the problem but it wasn't.

I get this too - mscorlib

Invalid character in a Base-64 string.[ at System.Convert.FromBase64String(String s) at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString) at System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState) at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState) at System.Web.UI.HiddenFieldPageStatePersister.Load() ]

The bottom line is
What do I do???? Can anyone help me figure this out and stop it from happening? I can give you access to the admin site, error logs, and whatever else you need. Thanks!

If I am being hacked, how do I stop it?

I will look at the traffic stats and see if I can pinpoint anything.

Marcus - Have you seen this before? The site is humming along then it slows way down and the products wont display. This happens 3-4 times a day for 5-10 minutes.

We are in a major bind with this. The site showed no items multiple times for 20-40 minutes over the weekend. There isn't any correlation to event errors. The traffic is not the issue. At 5:26AM our time was one of the instances and traffic was very low. There has to be something causing this. ANYONE??? PLEASE HELP!!! Our next avenue is dumping BV and moving to a yahoo store. Thanks!

Loosing 3,350 Google links is most likely not a solution.

Your site needs to be moved off of this current server.
Someone on the server is hogging resources.
The only true way to test your application is to isolate it.

You looked at your Alexa Stats lately
Time on site - up 132%
Pageviews/User - up 150%
Pageviews - up 560%
Reach - up 170%
Traffic Rank way up

It's time to make some adjustments for growth here.

This is a custom site written by Resposio. This issue has only started within the last few weeks. Nothing has changed on our side, programming, etc., except to add a google data feed. There has been no surge in orders and the traffic increase does not correlate with the down times. Believe me, I do not want to go to the huge hassle of switching to yahoo store. I have trouble believing this is a traffic issue enough to merit a dedicated server and several we have consulted agree with this. Perhaps we could move to a dedicated on a trial basis to see if it solves the problem? If that solves it we would be thrilled to pay the extra $200/mo.

I am concerned we are being hacked. If someone is doing some of the things with the SQL suggested by Marcus, it is not us.

"If the sql server does not respond in time to a query then the web site would show no products." That is definitely the problem, the question is why? Especially at 5AM?

Hi All,
Does anybody managed to sort display products issue for single category? I have the same problem, the category has 10k+ products. When I hit that category blank area is displayed... After some research I've found that it happens because of SQL timeout 30 seconds after hit. Stored procedure is bvc_Product_ByCategory_s. When I execute this stored procedure in SQL Server Management Studio with same category bvin it throws same timeout error after 30 secs. The most interesting is when I click modify stored procedure and hit execute without any changes - !!!problem disappears!!! but after a couple of days it appears again... Any ideas?

Could always add some Ajax to check inventory on a per item basis if you wanted. That's what I suggested to one client with a similar issue.