A well known issue is that if one installs from the 98 CD and then copies in their old email files, OE will cough up a notice just like you posted. The older version OE can't digest the newer format email files.
Sometimes, upgrading the IE to the version you had last works.
Bob
Amd 500 cpu
pcchips m598lmr Board
128 Meg ram
Windows 98se
8 Gig hd
I just reformatted the drive for the second time. Everything went well. When I logged onto the internet and started outlook express I get a message that says "This program has performed a illegal operation and will be shut down"
Here is the detail:
MSIMN caused an invalid page fault in
module <unknown> at 0000:00000015.
Registers:
EAX=00000070 CS=0167 EIP=00000015 EFLGS=00010286
EBX=8762f00c SS=016f ESP=0056896c EBP=00568a74
ECX=00e069cc DS=016f ESI=cc69e000 FS=3f57
EDX=802edebc ES=016f EDI=87227960 GS=3626
Bytes at CS:EIP:
ff 00 f0 79 ea 00 f0 21 ea 00 f0 00 00 00 d0 28
Stack dump:
00568970 0000016f 8734800a 00000002 87227a78 87347a69 87227a78 87227960 87227b50 87347b20 87227960 87227a78 00000000 00568a40 87227b50 87347ad9
I have no problem browsing the internet or running other programs. I have used win98 disk to reformat numerous times and have neve had this happen befoe. Any thoughts?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic