Magixien has posted an important announcement on PSPGen's site regarding the release of their much-awaited 5.03GEN-B for HEN (PSP-3000). Unfortunately, it's been delayed due to a "last minute bug".
Not to worry, though. The delay won't be for too long, and the bug isn't that much of a problem. It's actually just a recovery bug, and it appeared last night. As Magixien explains;
This is not a problem with the CFW but a recovery bug. If you remember, the recovery of 5.03GEN-A already had a problem: all option lines were shuffled. The correction of this problem comes with another bug in some options like the "use version.txt" which doesn't work anymore and prevents the launch of the MGS.
Between a partial release with a quick future update and an actual full working release, they opted on the latter. As such, you will be getting the release tomorrow night. It's just for a little while, so I'm sure you guys can wait it out.
Thanks to cmbeke for the tip!