FWSM NAT translation problem

Hi Group, 

I'm using FWSM 1.1(3) version and I have a question regarding FWSM NAT 
translation. 

I have used extended translation as shown below. 

static (inside,outside) tcp 10.100.100.45 7864 10.15.0.45 7864 netmask 
255.255.255.255
static (inside,outside) tcp 10.100.100.46 7864 10.15.0.46 7864 netmask 
255.255.255.255

Since these external IP addresses (10.100.100.45 and 46) are mapped to real 
servers 10.15.0.45 and 46 with only 7864 ports, it is not mapping to anything 
else for example ICMP. 

PROBLEM: I'm unable to ping 10.100.100.45 and 10.100.100.46 from outside world. 

Show xlate shows below output on FWSM:

PAT Global 10.100.100.45(7864) Local 10.15.0.45(7864)
PAT Global 10.100.100.46(7864) Local 10.15.0.46(7864)

I have the following access-list statements:

access-list acl_out permit icmp any host 10.100.100.45 
access-list acl_out permit icmp any host 10.100.100.46


FYI: If I replace the above static statements with the following simple static 
statements, ICMP reply will work fine from outside world. 

static (inside,outside) 10.100.100.45 10.15.0.45 netmask 255.255.255.255
static (inside,outside) 10.100.100.46 10.15.0.46 netmask 255.255.255.255


Please let me know how to fix this ICMP problem when I have the following 
static statements.

static (inside,outside) tcp 10.100.100.45 7864 10.15.0.45 7864 netmask 
255.255.255.255
static (inside,outside) tcp 10.100.100.46 7864 10.15.0.46 7864 netmask 
255.255.255.255


I should be able to ping 10.100.100.45 and .46 from outside world. 

NOTE: IP addresses are fictitious 

Thanks in advance.
Shekar