Outlook and secure remote on xp "HELP!!!!!"

[Meli]

i have windoes xp pro and office xp pro i use secure
remote "checkpoint vpn" to connect to my office i have
seen this many times before once i connect to the vpn i
am able to use all of my other applictaions threw my vpn
except for outlook it prompst me for my username passwor
and domain which i have tried we even used the admin it
comes backand says the credentials are incorrect i have
seen this on many of my users i have no clue what to do i
have reinstalled outlook checkpoint i really dont know
where to look . im not sure if it is OUtlook windows or
chekcpoint i need help i would appreciate it very much
thanks
mel