Right, spiral knight's won't start. I normally play through steam but that's recently stopped working too. I can't use the online launcher, installing it from SK website doesn't work either... What happens is when i launch spiral knights from steam or from the version installed from the SK website the logon screen comes up for a split second and then closes again. The online launcher just doesn't work at all which is really weird. I've been able to play through steam for quite a while before this issue. All my friends can still play it as well. I've tried deleting every trace of SK, Java and steam too, but nothing seems to work. I've also tried disabling AVG and Windows Firewall. I know i can run this game because i have in the past. Specs are as follows :
AMD Phenom ii 3.4ghz quad core
4GB 1600mhz DDR3 RAM
ATI Radeon 5870 1GB GDDR5
500 GB hard drive, not even half used up right now...
If anyone can shed any light it would be highly appreciated :D
Look in the SK directory for an hs_errPID####.log file. Could be something as minor as an autoupdate in AVG or Windows that slipped in under your nose, or even changes in anti-malware