OK, before you ask:
I have fully updated java, steam, spiral knights etc. I've used steam to verify the integrity of the game files, and I've searched the forum and the internet for solutions. I've found none. I'm using Windows 7 x64. When I run the game, if the Steam Overlay is enabled it crashes and windows says it's stopped working and gives the following information:
Problem signature:
Problem Event Name: APPCRASH
Application Name: javaw.exe
Application Version: 6.0.250.6
Application Timestamp: 4da6bb44
Fault Module Name: StackHash_b4ee
Fault Module Version: 0.0.0.0
Fault Module Timestamp: 00000000
Exception Code: c0000005
Exception Offset: 715d0000
OS Version: 6.1.7600.2.0.0.256.1
Locale ID: 1033
Additional Information 1: b4ee
Additional Information 2: b4ee5de6a2322745523997a782b35692
Additional Information 3: 277e
Additional Information 4: 277e19c30fbd5f6bb531ec9e027c37c3
This occurs ONLY with the steam overlay enabled. If I disable, the game will run fine, I just can't purchase energy. In fact, I'm pretty sure in-game is the only way steam players can purchase CE from Three Rings, so I'm quite literally unable to fork over any of my cash until this issue is resolved.
Exception Code: c0000005 is a memory access violation error. I'm a bit fuzzy on how it works, but the Overlay acts as wrapper that assists in the launch and hooks into the video drivers so it can inject the overlay into the game window. Because of the way it works, it'll run into problems in situations where Windows DEP is too strict, or an anti-virus is blocking the action thinking its malicious activity. It could also be caused by damaged files in the Steam client itself.
If you look at the windows event logs, it should show the crash and location of a report file. There are tools to dissect the file to find out more about why it crashed, but usually won't tell you the actual cause..... and we may not need to go that far to figure it out.
Anyway, the usual approach is to first make sure the overlay works with other games. Next disable any anti-virus, antispyware, scanners, security software, uppers, downers, or anything that can inject an on-screen display (MSIafter burner, FRAPS, etc), to try and figure out whats interfering with it. If nothing works, you can try refreshing your Steam files using the instructions below
Refresh steam - Note that it also resets your profile on the client, so you'll have to login again and give it a little while to recache all the icons. The library shouldn't be affected. https://support.steampowered.com/kb_article.php?ref=3134-TIAL-4638
If that still doesn't work, then something could be wrong with the system. A full spyware/AV scan by an external scanner would be prudent (like superantispayware or Malwarebytes). From there on out, it gets more complicated.