I confirmed Auto Upload continues to work for either 3G or WiFi, if the connection is solid. However, I was able to reproduce the issue on my own Android phone after letting my wifi lease expire, making the network connection appear on in my device status bar and to Photoshop Express, but functionally making it network access unavailable. (Even though 3G data was on, this did not help.)
Try these trouble-shooting steps:
1) force stop Photoshop Express, using Settings > Applications > Manage Applications > Running > Photoshop Express
2) turn off all WiFi connections available to you, and then re-enable them (forcing connections to reset)
3) launch Photoshop Express, and ensure you are signed into Photoshop Express Online, and also ensure Auto Upload is still enabled in Settings
4) try snapping some new photos, and see if they now auto-upload to Photoshop.com
If this doesn't help, repeat these steps, but try disabling/enabling 3G data instead of WiFi.