Hi, I recently upgraded to Studio 2015 from Studio 2011. I never had a problem opening an HTML file with Studio 2011 but since this morning, I cannot open an HTML file with Studio 2015. I can open other HTML files but not this one. The file that can't be opened can be opened in Adobe Dreamweaver or in Chrome so it's not corrupted.

The short error message says "Value cannot be null. Parameter name: input" 

The long error message is below.

Thanks for any help you can provide, my deadline is today, argh!

<SDLErrorDetails time="2/16/2016 9:09:34 AM">
<ErrorMessage>Value cannot be null.
Parameter name: input</ErrorMessage>
<Exception>
<Type>System.ArgumentNullException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type>
<ParamName>input</ParamName>
<HelpLink />
<Source>System</Source>
<HResult>-2147467261</HResult>
<StackTrace><![CDATA[ at System.Text.RegularExpressions.Regex.Matches(String input)
at System.Text.RegularExpressions.Regex.Matches(String input, String pattern)
at Sdl.FileTypeSupport.Filters.Html.Services.EntitiesConversionService.ForwardEntitiesConversion(String text)
at Sdl.FileTypeSupport.Filters.Html.Services.InlineEntityPlaceholderService.BuildSubParagraphUnitReference(Attribute attribute)
at Sdl.FileTypeSupport.Filters.Html.Services.InlineEntityPlaceholderService.AddLocalizableProperties()
at Sdl.FileTypeSupport.Filters.Html.Services.InlineEntityPlaceholderService.CreatePlaceholderFrom(Entity entity, HtmlParserElement htmlParserElement)
at Sdl.FileTypeSupport.Filters.Html.Consumers.Parser.InlineEntityConsumer.Consume(Entity entity, HtmlParserElement htmlParserElement)
at Sdl.FileTypeSupport.Filters.Html.Routes.Parser.InlineEntityRoute.Handle(Entity entity)
at lambda_method(Closure , IMessage )
at Sdl.FileTypeSupport.Filters.Html.Infrastructure.Dispatcher.Publish(IMessage message)
at Sdl.FileTypeSupport.Filters.Html.Parser.EntityParsed(Entity entity)
at Sdl.FileTypeSupport.Filters.Html.Services.ParserService.Publish(Entity parsedEntity)
at Sdl.FileTypeSupport.Filters.Html.Services.ParserService.Parse()
at Sdl.FileTypeSupport.Filters.Html.Parser.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.FileExtractor.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.MultiFileConverter.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.MultiFileConverter.Parse()
at Sdl.ProjectApi.AutomaticTasks.Conversion.ConversionTask.ProcessFile(IExecutingTaskFile executingTaskFile)
at Sdl.ProjectApi.AutomaticTasks.AbstractFileLevelAutomaticTaskImplementation.Execute()]]></StackTrace>
</Exception>
<Environment>
<ProductName>SDL Trados Studio</ProductName>
<ProductVersion>12.0.0.0</ProductVersion>
<EntryAssemblyFileVersion>12.0.4961.2</EntryAssemblyFileVersion>
<OperatingSystem>Microsoft Windows 7 Ultimate </OperatingSystem>
<ServicePack>Service Pack 1</ServicePack>
<OperatingSystemLanguage>1033</OperatingSystemLanguage>
<CodePage>1252</CodePage>
<LoggedOnUser>Meme-PC\Meme</LoggedOnUser>
<DotNetFrameWork>4.0.30319.34209</DotNetFrameWork>
<ComputerName>MEME-PC</ComputerName>
<ConnectedToNetwork>True</ConnectedToNetwork>
<PhysicalMemory>8351612 MB</PhysicalMemory>
</Environment>
</SDLErrorDetails>