Starting last night, Apple blocked the signing of SHSHs for iOS 4.0.1/3.2.1, so if you failed to save a SHSH for these 2 versions of iOS, then you will no longer be able to restore iPad/iPhone/iPod Touch- of yours to the respective versions. If in Cydia the message "Pending TSS Request" was displayed but you saved SHSHs with TinyUmbrella, then you can rest easy because Cydia has your SHSH, but if you had that message and you did not save SHSH with TinyUmbrella, then it is possible that you will be left without SHSH.
Apple continued to sign SHSHs for 4.0.1/3.2.1 for quite some time after the release of iOS 4.0.2, which is a bit strange, considering that they usually block signing SHSHs for older iOS immediately after the launch of a new one.
SHSH files are unique files for each phone, without which you CANNOT restore to iOS 4.x regardless of which iPhone/iPod Touch you have, nor to iOS 3.x for iPad/iPhone 3GS/iPod Touch 3G.
