One of my current clients is making the transition to Sitecore 8. This went reasonably well as we decided to do a fresh installation rather than follow the upgrade path and then copy any content in manually.
What we weren’t prepared for was a number of errors using Sql Server and IIS. Specifically we were getting heap exceptions with system.data.dll and ntdll.dll. However, what was funny was that these errors weren’t occuring on everyones systems. In fact the only repeatable thing was sporadic database issues with connectivity.
After some investigation we found that we were on .NET 4.5.1 and this has some known issues. So if you’re getting issues with IIS, the worker process or with the system.data dlls then this is one thing to look into.
Needless to say we did a test installation on a working system (well one with the least amount of issues) and this ran ok. Then we rolled it out to the other systems and this fixed our system. You can find out more about the list of known issues on the Microsoft support site.
The .Net 4.5.2 update is a web installer so you’ll need Internet access for any machine you’re updating.