Well, after much trial and error I think I've found a way, at least for me, around this little problem. I loaded up the pure RELOADED version of the game that the crack was from, and which mische seems to have no problems with. Now, before anyone bans me note that I do own the original, and it shouldn't matter which copy I use, mine or the RELOADED one, since I do own the original CDs.
After having installed the RELOADED version I still had the same problem with the weapons disappearing after reloading a level. I had just restarted the game, loaded a level, aborted, then loaded a different level. This is when I noticed something odd. If I load the first save (the one that has the intro in it, and which is the one for start of the overall missison) then load the last save game (in this case mission #4) I will start that mission with the M4 (which is the starting weapon for the first save btw). Now, I don't know about you, but this is pissing me off. At least this time I have a decent weapon with plenty of ammo, but I should also have the AK47, and AKU. BTW: for those that have made it to the oil rig, load up the first level, then load an older one (like the 4th one). You'll notice that you have both he M4 AND the Snpier rifle. Go figure.
Oh well.. I can wait... I still have my Xbox version, and now I have this work around if I decide to play the PC version.