Today, about one month after Microsoft Exchange Server 2010 RTM, Microsoft released Update Rollup 1. The following fixes are included in this RU:

• 977439 Exchange Server 2010 users cannot open certain attachments when they access their mailboxes by using Outlook Web App
• 977551 Meeting requests that are sent to a room mailbox are not processed in Exchange Server 2010
• 977552 Exchange RPC Client Access service crashes in the Handler.dll that is located on an Exchange 2010 Client Access service server
• 977553 Exchange RPC Client Access service crashes in Parser.dll on the Exchange Server 2010 CAS server
• 977554 The subject or body of a message that is hosted in an Exchange Server 2010 mailbox is not set as expected
• 977555 The message body is inaccessible when the property conversion from PR_BODY_HTML to PR_BODY fails
• 977556 The body text of an e-mail message is invisible after you create exceptions for a recurring appointment or for a recurring meeting by using a CDO application together with Exchange Server 2010
• 977557 An E_FAIL error occurs when you create an exception to a meeting request by using a CDO application for a Microsoft Exchange Server 2010 mailbox
• 977558 A folder name is not changed when you try to move and then rename the folder in an Exchange Server 2010 mailbox by using the CopyFolder method of the IMAPIFolder interface
• 977559 The location of a meeting or an appointment is not updated on an Exchange Server 2010 mailbox
• 977560 Update fails when you use a CDO application to update a recurrence task on Exchange Server 2010
• 977561 VSS backup process stops responding when you try to perform a Volume Shadow Copy Service (VSS) backup for Exchange Server 2010 databases

The knowledgebase article can be found here. You can download Rollup 1 directly from here.