VB6 repeated crashes ** Unresolved **

[maxl]

Here's the problem : 90 % of the time i close a certain mdi child form (I don't do any subclassing in this form) in my program, VB crashes. This only happens when I run my program from VB, the compiled version works just fine.
Here'S the detail of the error message I get :

VB6 a causé une défaillance de page dans
 le module KERNEL32.DLL à 017f:bff7b9f6.
Registres :
EAX=7fc39e61 CS=017f EIP=bff7b9f6 EFLGS=00010202
EBX=007ffe28 SS=0187 ESP=00700000 EBP=00700028
ECX=00701dd8 DS=0187 ESI=00000001 FS=3407
EDX=00000001 ES=0187 EDI=8175b9d4 GS=0000
Octets à CS : EIP :
57 89 65 e8 75 04 33 c0 eb 54 85 c0 74 4b c7 45 
État de la pile :
00000001 007ffe28 7fc39e61 00000001 007ffe28 7fc39e61 00701dd8 bffc05b4 bff79250 ffffffff 00701de8 bff7ce23 7fc39e61 00000001 7fc33046 7fc39e61

Quick french/english transalation :
VB6 has caused a page failure in the KERNEL32.DLL at 017f:bff7b9f6
Registres = Registers
Octets = Byte
État de la pile : State of the stack

Win 98( ), VB6 SP5

Any Idea what might be the cause of this ?? Thanks.