Access was never intended to be run across a WAN-type setup (which is what you're working with), and you'll find no end of troubles if you insist on making it try to do so. Access 2007 uses the ACE database engine, which is a "file server" type of database. That sort of db has no builtin processing engine, so ALL work must be performed by the workstation. This means that every time you open a form, or a report, Access must pull ALL those tables across the (very-very-very slow) connection, parse them, and then present your data. On average, a typical WAN connection is about 100 times slower than a standard office network; when dealing with internet hops, you can bet that speed is faaaaar worse than that. Access cannot survive in that scenario, and you'll quickly find yourself dealing with corrupt and/or lost data, corrupt forms, etc etc.
You have some options:
1) Move to a Terminal Server or Citrix setup. This can be expensive to setup and maintain, but will provide you with very robust and reliable usage for your off-site users.
2) Use a web-based service like
www.eqldata.com. I've never used them, and don't know of anyone who has, so please don't take this as any sort of recommendation. I'm just throwing it out there ;). Services like this cost you up front, and in monthly fees.
3) Rewrite the app to use a web-based interface (i.e. ASP.NET, Perl, PHP, etc etc). This is a good solution, but it will obviously require you to be knowledgable in those languages, and will obviously set back your deployment date.
4) Move your data store to SQL Server, MySQL, Oracle, etc etc and rewrite your FE to take advantage of that platform. This can be a massive undertaking, since in most cases you would need to do a ground-up rewrite - and it you're gonna do that, and you must support remote users, then you would be wise to consider #3.
