Why has my SD card stopped being detected on Xperia Mini Pro and other phones but still working on PCs?

A

AC Question

why my SD card stopped being detected on Xperia Mini Pro and other phones but still working on PCs?

I have an Xperia Mini Pro and I'm short of space for apps.
I have browsed for a solution and found several (Link2SD, and others) that require rooting.
I've rooted it with the app eroot and worked fine.
Then I followed the steps to create a secondary partition on the SDHC Class 1 kingston card my phone already had.

(I followed the talk.sonymobile.com/t5/Xperia-mini-pro/Save-Applications-on-Micro-SD-Card/td-p/129332 procedure)

When I created the secondary partition with the software mentioned there, and put that back on the phone, it stopped being detected.

I formatted it again with PC (with FAT32 formatting) and I tried putting the card on anohter Android phone and also did not work, but everytime I put it on the PC it is recognized and I can copy files to it.

Any idea?