I'm working on extending the Content Query webpart to fetch the content from across the Site Collections. I've to show up the content from 3 different site collections (SiteCollA, SiteCollB & SiteCollC).

Since the query remains the same for these 3 content sources, I build the query first in my code using CrossListQueryInfo object.

CrossListQueryInfo queryInfo = new CrossListQueryInfo();
and assign all the properties of CrossListQueryInfo.

Now I pass this query to the three content sources, using separate CrossListQueryCache for each content source and merge the DataTable.

for e.g.
CrossListQueryCache queryCacheSiteCollA = new CrossListQueryCache(queryInfo);
dtResults.Merge(queryCacheSiteCollA.GetSiteData(<SPSite object of SiteCollA>));

CrossListQueryCache queryCacheSiteCollB = new CrossListQueryCache(queryInfo);
dtResults.Merge(queryCacheSiteCollB.GetSiteData(<SPSite object of SiteCollB>));

CrossListQueryCache queryCacheSiteCollC = new CrossListQueryCache(queryInfo);
dtResults.Merge(queryCacheSiteCollC.GetSiteData(<SPSite object of SiteCollC>));

I'm experiencing a strange behavior, If I set the UseCache property of CrossListQueryInfo as false, then I get the results immediately, of all three site collections.

Whereas, if I set the UseCache property of CrossListQueryInfo as true, then

On first page load, I got File Not Found Exception on webpage. After debugging, i found out that I got results of only first Site Collection i.e. SiteCollA, and got an exception at queryCacheSiteCollA.GetSiteData(<SPSite object of SiteCollA>), which says "Invalid URL".

On second page load, I again got File Not Found Exception on webpage. After debugging, i found out that I get results of first Site Collection i.e. SiteCollA, and second Site Collection i.e. SiteCollB. I got an exception at queryCacheSiteCollC.GetSiteData(<SPSite object of SiteCollC>), which says "Invalid URL".

On third page load, finally I got the correct result set on webpage.

Have you experience anything like this, while doing custom aggregation using CrossListQueryInfo from across sites?
& plz let me know What value did you use for the property UseCache of CrossListQueryInfo?