I just downloaded the trial of the WPF controls and am seeing an issue.
My goal is to have the SyntaxEditor embedded within a 3rd party grid control (XamDataGrid). But I have reproduced the issue by using a ControlTemplate for a TextBox. The space key is not working. You can see that the settings are all identical for the two SyntaxEditor's. The only difference is the ControlTemplate.
<Window x:Class="XamDataGridWithIntelliPrompt.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:igDP="http://infragistics.com/DataPresenter"
xmlns:syntaxeditor="http://schemas.actiprosoftware.com/winfx/xaml/syntaxeditor"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<Style TargetType="TextBox">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TextBox">
<syntaxeditor:SyntaxEditor IsMultiLine="False" >
<syntaxeditor:EditorDocument>
<syntaxeditor:EditorDocument.Language>
<syntaxeditor:CSharpSyntaxLanguage />
</syntaxeditor:EditorDocument.Language>
</syntaxeditor:EditorDocument>
</syntaxeditor:SyntaxEditor>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
<StackPanel>
<syntaxeditor:SyntaxEditor IsMultiLine="False" >
<syntaxeditor:EditorDocument>
<syntaxeditor:EditorDocument.Language>
<syntaxeditor:CSharpSyntaxLanguage />
</syntaxeditor:EditorDocument.Language>
</syntaxeditor:EditorDocument>
</syntaxeditor:SyntaxEditor>
<TextBox />
</StackPanel>
</Window>