Firstly check how the drives look under fdisk by doing :
/sbin/fdisk -l /dev/hdb
This should tell you if there are any issues such as the partition becoming hidden. As said before if it really is an logical partition the 'parent' extended partition would be /dev/hdbx where x is 1 to 4 in the order the physical partition was created, i.e. it could indeed be /dev/hdb1. However, the actual logical (data) partitions within the extended partition begin /dev/hdb5 onwards. You would mount the logical partition not the extended partition.
Check the boot messages via dmesg to see how the system sees the partition table as it boots - logical partitons are shown within <> brackets.
Did you reconnect it to the same ide (first) controller as slave ? If not it could be hdc or hdd. What does seem odd is if you mounted a partition as -t ext2 and it didn't complain but you found nothing.
As said before, if it mounts without complaint and a 'df' shows the filesystem as large and empty you have a big problem!!
The filesystem should mount more or less instantaneously so theres something wrong if it takes a whole minute!
The only similar problem I had was upgrading from rh6.2 t rh7.0 due to the use of redhat's use of 'labels' in /etc/fstab instead of specific /dev/hdxx entries. This was supposed to help moving drives around as it's more 'logical' than 'physical'. You might want to check whats in you /etc/fstab for that drive.
Best of luck..