Hello Tina,
Thank you for your reply. Using your sample, I have been able to determine that this issue seems to only happen when the MediaPlayer is contained in a floating RadPane, which is necessary for our application. I have modified the sample project you provided to demonstrate this, and since I cannot upload the project the modified XAML is below. Leaving the window docked as it is initially, if you press play, click the button you added, and then press pause, it behaves as expected. However, if you make the window floating and do the same thing, pressing the pause button causes the MediaPlayer to unload, reload, and begin the playback of the video at the beginning.
<Grid>
<telerik:RadDocking>
<telerik:RadDocking.DocumentHost>
<telerik:RadPaneGroup>
<telerik:RadPane Header="RadPaneHeader">
<telerik:RadPane.Content>
<telerik:RadMediaPlayer x:Name="player"
AutoPlay="False" Style="{StaticResource RadMediaPlayerStyle}">
<telerik:RadMediaItem.Header>
<StackPanel Orientation="Horizontal">
<StackPanel Margin="8">
<TextBlock FontWeight="Normal" Text="Name: " />
<TextBlock Margin="4"
FontWeight="Bold"
Text="Optimizing for Performance with the Windows Performance Toolkit" />
</StackPanel>
<StackPanel Margin="8">
<TextBlock FontWeight="Normal" Text="Genre: " />
<TextBlock Margin="4"
FontWeight="Bold"
Text="Tech Video" />
</StackPanel>
</StackPanel>
</telerik:RadMediaItem.Header>
</telerik:RadMediaItem>
<telerik:RadMediaItem.Header>
<StackPanel Orientation="Horizontal">
<StackPanel Margin="8">
<TextBlock FontWeight="Normal" Text="Name: " />
<TextBlock Margin="4"
FontWeight="Bold"
Text="Networking and Web Services in Silverlight" />
</StackPanel>
<StackPanel Margin="8">
<TextBlock FontWeight="Normal" Text="Genre: " />
<TextBlock Grid.Column="1"
Margin="4"
FontWeight="Bold"
Text="Tech Video" />
</StackPanel>
</StackPanel>
</telerik:RadMediaItem.Header>
</telerik:RadMediaItem>
</telerik:RadMediaPlayer>
</telerik:RadPane.Content>
</telerik:RadPane>
</telerik:RadPaneGroup>
</telerik:RadDocking.DocumentHost>
</telerik:RadDocking>
</Grid>