Version:           1.9.5 (using KDE 3.5.5 "release 45.2" , openSUSE 10.2)
Compiler:          Target: i586-suse-linux
OS:                Linux (i686) release 2.6.18.2-34-bigsmp

After upgrading I used the file-->import, "Import from kmail" to migrate my old folder to the new version of kmail.
When the migrated folders appeare in the window (ok, folders sent and received didn't appear)I moved some from the migration folder into the "Loca folders". But when selecting another folder kmail hangs. CPU goes to 100% and kmail has to be killed. GUI hangs too. 
Using strace I got the following output:

select(19, [3 4 5 6 8 18], [], [], {0, 999765}) = 0 (Timeout)
gettimeofday({1170612759, 201290}, NULL) = 0
ioctl(4, FIONREAD, [0])                 = 0
gettimeofday({1170612759, 201446}, NULL) = 0
select(19, [3 4 5 6 8 18], [], [], {0, 0}) = 0 (Timeout)
gettimeofday({1170612759, 201607}, NULL) = 0
gettimeofday({1170612759, 201740}, NULL) = 0
gettimeofday({1170612759, 201831}, NULL) = 0
ioctl(4, FIONREAD, [0])                 = 0
gettimeofday({1170612759, 201972}, NULL) = 0
select(19, [3 4 5 6 8 18], [], [], {0, 999768}) = 0 (Timeout)
gettimeofday({1170612760, 205220}, NULL) = 0
gettimeofday({1170612760, 205328}, NULL) = 0
gettimeofday({1170612760, 205413}, NULL) = 0
ioctl(4, FIONREAD, [0])                 = 0
gettimeofday({1170612760, 205557}, NULL) = 0
select(19, [3 4 5 6 8 18], [], [], {0, 999771}) = 0 (Timeout)
gettimeofday({1170612761, 209229}, NULL) = 0
gettimeofday({1170612761, 209382}, NULL) = 0
gettimeofday({1170612761, 209475}, NULL) = 0
ioctl(4, FIONREAD, [0])                 = 0
gettimeofday({1170612761, 209625}, NULL) = 0
select(19, [3 4 5 6 8 18], [], [], {0, 999757}) = 0 (Timeout)
gettimeofday({1170612762, 213145}, NULL) = 0
gettimeofday({1170612762, 213258}, NULL) = 0
gettimeofday({1170612762, 213341}, NULL) = 0
ioctl(4, FIONREAD, [0])                 = 0