It appears the 1.5.4 release is buggy. I've tested both 1.5.4 and 1.5.4.1 QT wallets, both crash when issued RPC commands.

I'm guessing this is why the remaining mining pools, exchanges and explorer are all still using the previous 1.5.3 version.

Here are download links to the 1.5.3 client if you'd prefer or need to run it (i.e for solo mining).

Windows: https://mega.nz/#!M1wgHbIJ!c4RayOQc0VKU1MwIbMRVC7vCJKLCAd1jWfoDCeAolNw
Sha256: 35f7c105cf2dee15f6c015ed760ad0f9ef8237957f93a7bea2560f2cf14c1fa3
MD5: 4086776924427bf01e9a1716cfdc5618
VirusTotal: https://www.virustotal.com/en/file/35f7c105cf2dee15f6c015ed760ad0f9ef8237957f93a7bea2560f2cf14c1fa3/analysis/

Mac OSX: https://mega.nz/#!M4hzxIqL!9E6hB2-wm0BLMvtFT0h5GutGwk_oKQnHOYTzAgUce_k
Sha256: a6eb77421852c53e939294f139bf80aeca3b0386600cb797170051f84e912128
MD5: 0fdf3c2a32f14f1a9d432cf625f57e17
VirusTotal: https://www.virustotal.com/en/file/a6eb77421852c53e939294f139bf80aeca3b0386600cb797170051f84e912128/analysis/

Source: https://github.com/DigitalHoldings/Globalcoin

You may also need to setup port forwarding on your modem/router if you're having trouble syncing. Allowing TCP connections on port 55789 will allow the 1.5.3 client to find nodes.