I am having the same problem with Hollywood Strings Diamond. I have the latest version of Play and the instrument updates and have been in communication with EW but so far have not had any joy. I've sent EW (at their request) a midi file this morning (unfortunately they don't have Sonar so I can't send them a full project). Curiously not all the patches behave the same. Sometimes they will play properly once and then play very quietly after that rather than not at all. Sometimes I can play the project a number of times before the patch stops playing. But it is quite frustrating. I'm currently running Sonar Platinum but previously had the same issues with X3. My PC is running Windows 7 64 bit, Intel Core i7 3.5GHz processor with 32 Gig RAM. My interface is an RME Fireface UCX connected via a Firewire PCIe card. I have the Hollywood Strings Diamond on a Samsung 1TB Evo SSD along with Hollywood Brass Diamond on the same drive. The Hollywood Brass instruments don't seem to misbehave. I also have Symphonic Orchestra Platinum and their Pianos and Storm Drum (on a 480GB Sandisk SSD) but these don't misbehave either. My OS is on another separate 480GB SSD and I have two 2GB SATA drives as well for data storage (including recorded audio tracks). Anyone with any clues?

This may not be good news, but I found Hollywood Strings completely unusable until I installed an SSD.  Hollywood only loads the first part of a sample into memory and then streams the rest from the disc.
 
If your hard drive is pretty empty (like 60% or more space available), you might get it to work OK, but I never had more than 40% free and I could never get decent results (plus the load time was horrendous).  I had to create separate projects for just the strings, freeze them, and them import the audio into the real project—and even that took several tries and didn't always work.
 
I installed a 1 TB SSD for Hollywood and Vienna and they work fine now.
 
I hope your issue is something that can be easily solved, but, for me, it was well worth the price for the SSD since I had a ton of money tied up in sample libraries I couldn't really use.
 
By the way, I got the Samsung Pro which costs a little more than the Evo, but I thought I might as well go big and get the problem solved once and for all.
 
http://www.newegg.com/Product/Product.aspx?Item=N82E16820147362
 
I also had to buy the hardware to convert the slot for the drive and I needed a power cable as well, but those were just a few bucks each.  A friend of mine is a hardware guy, so he did the install.

  Hello, Farmer George here,
    I am having the exact problem Ben at the top of the page was having.
      When I load any east west modules in Sonar Platinum I have no problems, as soon as I load Hollywood strings gold problems start. I can play a melody and then record it, I play it back fine but as soon as I rewind the music the strings sounds of the module stop playing while the other modules are ok and playing normally. I downloaded the latest PlayFix   5.1 but still have the problem with the strings.
      Can anyone help on this?
                                              farmer George
                                                                  New Jersey

Farmer George, a good place to start is by providing some details on your system specs.  Until then we don't have a clue what you're up against.

Ok  Farmer George back with more info.
               Dell XPS    I7 processor   24 gig ram  Steinberg UR22mk2 sound card
 When I load any east west modules in Sonar Platinum I have no problems, as soon as I load Hollywood strings gold problems start. I can play a melody and then record it, I play it back fine but as soon as I rewind the music the strings sounds of the module stop playing while the other modules are ok and playing normally.