outputcache limitations?

[Vassilis T. via .NET 247]

The following piece of code, when on a heavily loaded server (more than 50 ASP.NET pages, most using outputcache with varybyparam, lots of users), will only cache the string - the output is not cached, as if the outputcache is ignored.
There is available RAM on the server.
Other pages are cached as expected.
On the development environment and on a test server, it works fine.

Are there any limitations to the .NET caching, apart from RAM availability? Should I reduce caching time on other pages, or remove caching from some pages to resolve the problem?

TIA


<%@ OutputCache Duration="10" VaryByParam="none"%>
<%
Response.write("outputcache:" & datetime.now.tostring("s") & "<BR>")
Dim atest As String
if cache("atest") is nothing then
atest=DateTime.Now.ToString("s")
Cache.Insert("atest",atest,nothing,DateTime.Now.AddSeconds(20),Cache.NoSlidingExpiration,CacheItemPriority.High,nothing)
else
atest=cache("atest")
end if
response.write("atest string:" & atest)
%>