Late Tuesday, Apple released the second beta version of the pending iOS 4.1 firmware, although the company has not said when the firmware will be generally available for its iPhone and iPod touch products.

Per Cult of Mac, this beta release of the iOS 4.1 software development kit, available at Apple’s iPhone Dev Center, comes about two weeks after the first one and arrives with speculation that the 4.1 software will fix some glitches for the iPhone 4 proximity sensors and introduce Apple’s promised Game Center social service.

The initial report states that the proximity sensor issue seems to have been fixed. “Previously, the iPhone was plagued with proximity sensor issues,” writes Jose Gutierrez. “It would constantly hang up calls when I held the phone next to my cheek. But after installing the iOS 4.1 beta 2 update this afternoon, I couldn’t force the iPhone to hang up calls when lifting it up to my face, no matter how hard I tried.”

He also says the new beta release includes a baseband update, “which seems to fix HSUPA upload speed issues, which slowed video and photo uploads to a crawl.”

According to several online accounts, the newest beta still does not support the iPad touch tablet. The iPad is running an earlier version of iOS.

Stay tuned for additional details as they become available.