SBS2003 -> 2011 Migration - Some Sharepoint Calendar Items not Showing in Calendar View but Show in All/Current Events

Bascially I've followed the Microsoft guide on SBS 2003 -> 2011 Migration. Performed it over the weekend to try and give zero downtime for users. It's pretty much worked fine except this issue. (I haven't imported the users into 2011 console/format yet but everything else complete)

This morning users reported a few recently added items to the shared calendar had vanished.

I still have the old version of companyweb on the old SBS 2003 (although it is not the original version, but the updated version on Sharepoint Services 3.0 as part of the migration).

Looking at the old version, I can see many entries missing on the new version. The bit that initally threw me was that all the entries that showed were by two users while all entries by the other users had vanished. However I eventually found one holiday entry spanning a few days that showed from a user where all her other entries had vanished.

Also from that I checked permissions across users and could not find any reason for differences.

After further investigation I noticed on the new Sharepoint, if I selected the All Events or Current Events view for the calendar, I could see all the calendar events - i.e. the missing ones returned.

I also tried enabling search on the site and then searching for one of the "missing" events. If I did this it finds it, but interestingly it also finds it on the correct page of the calendar, but if I select this it takes me to the calendar page without the event.

Health Analyser only moans that Databases exist on servers running Sharepoint Foundation and Built-in accounts are used as application pool or service identities.

The database schema versions appear to have correctly updated:

Database Schema Versions

Microsoft.SharePoint.Upgrade.SPContentDatabaseSequence Current Schema Version: 4.0.145.0, Maximum Schema Version: 4.0.145.0

Microsoft.SharePoint.Upgrade.SPContentDatabaseSequence2 Current Schema Version: 4.0.8.0, Maximum Schema Version: 4.0.8.0

Microsoft.SharePoint.Administration.SPContentDatabase Current Schema Version: 14.0.4762.1000, Maximum Schema Version: 14.0.4762.1000

Any help on this would be very greatfully appreciated.

This is my first question on here so if it does need any altering I would be grateful for help/constructive criticism.

Edit: Downloaded a copy of sharepoint designer, using this to look at the shared diary, all the "missing" entries are present!